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New papers on 2025-05-20
Feed: cond-mat updates on arXiv.org
Authors: Sonal Maroo, Leonardo Coello Escalante, Yizhe Wang, Matthew P. Erodici, Jonathon N. Nessralla, Ayana Tabo, Takashi Taniguchi, Kenji Watanabe, Ke Xu, David T. Limmer, D. Kwabena Bediako
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11619v1 Announce Type: new
Abstract: The activation free energy of electron transfer (ET) reactions is governed by a crucial parameter: the reorganization energy. In heterogeneous ET at electrified solid-liquid interfaces, it is presumed that only factors in the electrolyte phase are responsible for determining the reorganization energy. Here, we demonstrate the contribution of the electronic density of states (DOS) of the electrode to the reorganization energy. Using van der Waals assembly of two-dimensional crystals, we tune the DOS of graphene and measure its impact on outer-sphere ET. We find the ensuing variation in ET rate arises from modulation in a reorganization energy associated with image potential localization in the electrode, which is dependent on the DOS. This work establishes a fundamental role of the electrode electronic structure in interfacial charge transfer.
Authors: Ilaria Maccari, Egor Babaev, Johan Carlstr\"om
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11630v1 Announce Type: new
Abstract: The possibility that nematicity induced by electron pairing could persist above the superconducting transition temperature represents a form of composite order, sometimes referred to as a vestigial nematic phase. However, it remains debated whether--and under what conditions--such a phase can emerge in realistic models of nematic superconductors. Recent analytical work [1] concluded that vestigial nematic phases and related mechanisms do not arise in commonly used models proposed, for example, for Bi2Se3-based candidates. To address this question, we perform large-scale Monte Carlo simulations of a three-dimensional Ginzburg-Landau model of a nematic superconductor. Consistent with the findings of Ref.[1], our numerical results confirm that the commonly considered models do not exhibit vestigial nematic phases or nematic-fluctuation-induced charge-4e superconductivity. In the second part of the study, we investigate a different class of models and show that, under restrictive conditions, vestigial nematic order can be stabilized by an alternative mechanism: intercomponent coupling mediated by a gauge field or the effects of strong correlations.
Authors: M. Tirgar, H. Barati Abgarmi, J. Abouie
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11652v1 Announce Type: new
Abstract: This study theoretically investigates the thermoelectric properties of magnetic topological insulators (TIs), with a focus on the effects of magnetic atom exchange interactions on the thermopower of their surfaces. Our findings demonstrate that interactions among magnetic atoms significantly enhance the Seebeck coefficient. The formation of magnetic clusters through exchange interactions increases the scattering of Dirac electrons, thereby improving the thermoelectric power factor. We conducted extensive Monte Carlo simulations across various configurations, including ferromagnetic and antiferromagnetic bulk materials, comparing magnetic clustering in Ising and Heisenberg models. Special attention was given to cluster definitions related to surface critical temperatures. Our analysis indicates that the size and number of magnetic clusters influence relaxation times, as well as electrical and thermal resistivities, ultimately affecting the thermopower. Optimized interlayer and intralayer interactions can elevate the surface thermopower of TIs to values comparable to those observed in antiferromagnetic ${\rm MnTe}$, renowned for its unique spin-based thermoelectric properties. This work highlights the potential of magnetic TIs for thermoelectric applications and sets the stage for future research.
Authors: Emmanouil K. Kokkinis, Andrey V. Chubukov
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11727v1 Announce Type: new
Abstract: We study pseudogap behavior in a metal near an antiferromagnetic instability and apply the results to electron-doped cuprates. We associate pseudogap behavior with thermal magnetic fluctuations and compute the fermionic self-energy along the Fermi surface beyond Eliashberg approximation. We analyze the spectral function as a function of frequency (energy distribution curves, EDC) and momentum (momentum distribution curves, MDC). We show that the EDC display pseudogap behavior with peaks at a finite frequency at all momenta. On the other hand, MDC peaks disperse within the pseudogap, ending at a gossamer Fermi surface. We analyze magnetically-mediated superconductivity and show that thermal fluctuations almost cancel out in the gap equation, even when the self-energy is obtained beyond the Eliashberg approximation. We favorably compare our results with recent ARPES study [K-J Xu et al, Nat. Phys. 19, 1834-1840 (2023)].
Authors: Ilja Fescenko, Raman Kumar, Thitinun Gas-Osoth, Yifei Wang, Suvechhya Lamichhane, Tianlin Li, Adam Erickson, Nina Raghavan, Tom Delord, Cory D. Cress, Nicholas Proscia, Samuel W. LaGasse, Sy-Hwang Liou, Xia Hong, Jose J. Fonesca, Toshu An, Carlos A. Meriles, Abdelghani Laraoui
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11728v1 Announce Type: new
Abstract: Two-dimensional (2D) magnets are of significant interest both as a platform for exploring novel fundamental physics and for their potential applications in spintronic and optoelectronic devices. Recent magnetic bulk measurements have indicated a weak ferromagnetic response in WS2 and theoretical predictions suggest that the edges of such flakes exhibit magnetization when at least one edge of a flake is partially hydrogenated. Here, we use room-temperature wide-field quantum diamond magnetometry to image pristine and Fe-implanted WS2 thin flakes of variable thickness, exfoliated from a bulk crystal and transferred to nitrogen-vacancy (NV)-doped diamond substrates. We provide the first direct evidence of edge-localized stray fields, growing linearly with the applied magnetic field and reaching up to 4.7 uT. Magnetic simulations using alternative models favor the presence of edge magnetization aligned along an axis slightly tilted from the normal to the WS2 flake plane. Our observations open intriguing opportunities on the use of WS2 for spintronics applications.
Authors: Qing-Ping Ding, Juan Schmidt, Jose A. Moreno, Sergey L. Bud'ko, Paul C. Canfield, Yuji Furukawa
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11732v1 Announce Type: new
Abstract: The relationship between antiferromagnetic (AFM) spin fluctuations (SF), nematic fluctuations, and superconductivity (SC) has been central to understanding the pairing mechanism in iron-based superconductors (IBSCs). Iron chalcogenides, which hold the simplest crystal structure in IBSCs, provide a good platform to investigate the relationship. Here, we report $^{77}$Se and $^{125}$Te nuclear magnetic resonance studies of FeSe$_{0.47}$Te$_{0.53}$, which is located close to a nematic quantum critical point (QCP), under pressures up to 1.35 GPa. Both the superconducting critical temperature and AFMSF were found to be enhanced under pressure, which suggests a correlation between SC and AFMSF in FeSe$_{0.47}$Te$_{0.53}$. However, the contribution of AFMSF to SC in FeSe$_{0.47}$Te$_{0.53}$ was found to be much less compared to that in FeSe$_{1-x}$S$_{x}$, suggesting that nematic fluctuations play a dominant role in the SC in FeSe$_{1-x}$Te$_{x}$ around the nematic QCP.
Authors: Olga Yu. Mazur, Yuri A. Genenko, Leonid I. Stefanovich
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.11819v1 Announce Type: new
Abstract: The stochastic analysis of the polarization domain structures, emerging after quenching from a paraelectric to a ferroelectric state, in terms of the polarization correlation functions and their Fourier transforms is a fast and effective tool of the materials structure characterization. In spite of a significant volume of experimental data accumulated over the last three decades for the model uniaxial ferroelectric triglycine sulfate, there were no theoretical tools to comprehend these data until now. This work summarizes the recent progress in understanding of the experiments by means of the original stochastic model of polarization structure formation based on the Landau-Ginzburg-Devonshire theory and the Gauss random field concept assuming the predominance of the quenched polarization disorder over the thermal fluctuations. The system of integrodifferential equations for correlation functions of random polarization and electric field turns out to be analytically solvable. The model provides explanations to a range of experimental results on the polarization formation kinetics including the time-dependent correlation lengths and correlation functions on the macroscopic spatial and time scales. Notably, it predicts the dependence of the ferroelectric coercive field on the initial disordered state characteristics, which can be controlled by quenching parameters like the initial temperature and the cooling rate, thus paving the way for tailoring the functional properties of the material.
Authors: G. Alatteili, L. A. Scafuri, E. Iacocca
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12011v1 Announce Type: new
Abstract: Magneto-toroidal artificial spin ices (MT-ASIs) are arrangements of nanomagnets that exhibit spontaneous toroidization. A ferrotoroidic order could have implications on the propagation of spin waves through this artificial spin ice, including the development of topological edge modes. Here, we numerically investigate the magnetization dynamics of an MT-ASI with and without spatial symmetry breaking. Through micromagnetic simulations, we compute the energies and ferromagnetic resonance spectra of the four lowest-order states, which exhibit ferrotoroidicity, antiferrotoroidicity, and no toroidicity. As expected, we find that the resonant modes split when spatial symmetry is broken. To determine whether our system exhibits topologically protected edge modes, we perform semi-analytical calculations to first estimate the ferromagnetic resonance and then compute the band structure. Our results show that symmetry-broken MT-ASIs are reconfigurable by magnetic field protocols, and that their band structures depend on magnetization state. Calculation of the Chern number indicates that the bands are topologically trivial in all cases, suggesting that the dynamic magnetic coupling is weak. The absence of a non-zero Chern number is proof of the weak dynamic coupling in ASIs, which must be addressed to unlock their full potential in magnonics applications.
Authors: Alexandre Krajenbrink, Pierre Le Doussal
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12034v1 Announce Type: new
Abstract: The weakly asymmetric exclusion process (WASEP) in one dimension is a paradigmatic system of interacting particles described by the macroscopic fluctuation theory (MFT) in the presence of driving. We consider an initial condition with densities $\rho_1,\rho_2$ on either side of the origin, so that for $\rho_1=\rho_2$ the gas is stationary. Starting from the microscopic description, we obtain exact formulae for the cumulant generating functions, and large deviation rate functions of the time-integrated current and the position of a tracer. As the asymmetry/driving is increased, these describe the crossover between the symmetric exclusion process (SSEP) and the weak noise regime of the Kardar-Parisi-Zhang (KPZ) equation: we recover the two limits and describe the crossover from the WASEP cubic tail to the $5/2$ and $3/2$ KPZ tail exponents. Finally, we show that the MFT of the WASEP is classically integrable, by exhibiting the explicit Lax pairs, which are obtained through a novel mapping between the MFT of the WASEP and a complex extension of the classical anisotropic Landau-Lifshitz spin chain. This shows integrability of all MFTs of asymmetric models with quadratic mobility as well as their dual versions.
Authors: Jianning Guo, Dmitrii V. Semenok, Ivan A. Troyan, Di Zhou, Yulong Wang, Yuzhi Chen, Su Chen, Kexin Zhang, Xinyue Wu, Sven Luther, Toni Helm, Andrey V Sadakov, Alexey S. Usoltsev, Leonid A Morgun, Vladimir M Pudalov, Viktor V Struzhkin, Xiaoli Huang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12062v1 Announce Type: new
Abstract: Strong magnetic fields provide a unique environment for investigating the fundamental properties of superconducting materials especially for hydride superconductors with large upper critical fields. Following this idea, we have investigated the effect of pulsed magnetic fields on covalent bismuth dihydride, successfully synthesized under pressure up to 211 GPa. The electrical resistance measurements indicate that the superconducting phase P21m BiH2 exhibits the highest superconducting critical temperature (Tc) of 70 K among MH2type hydrides apart from H2S. The electrical transport experiments under both pulsed (up to 50 T) and steady magnetic fields (up to 16 T) for P21m and C2m BiH2 indicate that the upper critical fields miu0Hc2(0) is 12 to 16 T are unusually low, much lower than that of clathrate-like metal polyhydrides with similar Tc. This is due to the unexpectedly high Fermi velocity in BiH2, about 1.1 106 m s, which allows to classify BiH2 as a soft molecular superconducting hydride with relatively weak vortex pinning. Measurements of the current voltage characteristics in the pulsed mode make it possible to experimentally establish the temperature dependence of the critical current density (the maximum Jc(0) is 10 kA mm2), which indicates the presence of two s wave superconducting gaps in BiH2 at 172 to 176 GPa: deltaL(0) is 6.9 1.2 meV and deltaS(0) is 1.5 meV.
Authors: Juan Pablo Carrillo-Mora, Moniellen Pires Monteiro, V. I. Marconi, Maria Luisa Cordero, Ricardo Brito, Rodrigo Soto
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12067v1 Announce Type: new
Abstract: The trajectories of microswimmers moving in narrow channels of widths comparable to their sizes are significantly altered when they encounter another microswimmer moving in the opposite direction. The consequence of these encounters is a delay in the progress of both swimmers, which can be conceptualized as an instantaneous effective backward displacement. Similarly, the modeling of tumble events in bacteria, which occur over a finite time, can be represented as an instantaneous effective displacement in addition to a change in direction. Such effective displacements can be incorporated directly into a kinetic theory for the partial densities of swimmers moving in the channel. The linear analysis of the resulting equation yields the critical density at which clusters emerge. The methodology is then applied to the case of soil bacteria moving in long channels of cross-section 1.8~${\mu}$m $\times$ 1.8~${\mu}$m. The tracking of the swimmers permits the straightforward acquisition of the effective displacements, which in turn allows the critical density (${\rho}_{\text{crit}}\simeq$ 0.10 bact/${\mu}$m) to be predicted prior to cluster formation. The advantage of this proposed approach is that it does not necessitate the determination of an effective density-dependent speed, which is a requisite of the standard motility-induced phase separation theory.
Authors: T. I. Weinberger, H. Chen, Z. Wu, M. Long, A. Cabala, Y. Skourski, J. Sourd, T. Haidamak, V. Sechovsky, M. Valiska, F. M. Grosche, A. G. Eaton
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12131v1 Announce Type: new
Abstract: The heavy fermion material UTe$_2$ hosts a suite of exotic superconducting phases, the most extreme of which resides in a narrow angular window of intense magnetic fields $>$ 40 T. Here we report that in the angular and field regime in which field-induced superconductivity is most robust, the normal-state resistivity exhibits a linear temperature dependence characteristic of strange metallicity, sharply contrasting with the Fermi-liquid behavior observed at low fields and away from this angular window. Through angle-dependent magnetotransport measurements in high magnetic fields, we find that the strange metal state is confined to a narrow angular range where field-induced superconductivity is also maximized, suggesting a shared underlying mechanism. These findings reveal a novel setting for strange metallicity - proximate to spin-triplet, field-induced superconductivity - and point to the presence of quantum critical fluctuations, likely of a magnetic origin. The coexistence of strange metallicity and putatively spin-triplet pairing challenges prevailing paradigms of non-Fermi-liquid phenomenology, and highlights UTe$_2$ as a unique platform for exploring the interplay between unconventional superconductivity and quantum criticality.
Authors: Felipe Hawthorne, Paulo R. E. Raulino, Ronaldo Rodrigues Pel\'a, Cristiano F. Woellner
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12140v1 Announce Type: new
Abstract: Machine learning interatomic potentials (MLIPs) offer an efficient and accurate framework for large-scale molecular dynamics (MD) simulations, effectively bridging the gap between classical force fields and \textit{ab initio} methods. In this work, we present a reactive MLIP for graphene, trained on an extensive dataset generated via \textit{ab initio} molecular dynamics (AIMD) simulations. The model accurately reproduces key mechanical and vibrational properties, including stress-strain behavior, elastic constants, phonon dispersion, and vibrational density of states. Notably, it captures temperature-dependent fracture mechanisms and the emergence of linear acetylenic carbon chains upon tearing. The phonon analysis also reveals the expected quadratic ZA mode and excellent agreement with experimental and DFT benchmarks. Our MLIP scales linearly with system size, enabling simulations of large graphene sheets with \textit{ab initio}-level precision. This work delivers a robust and transferable MLIP, alongside an accessible training workflow that can be extended to other materials.
Authors: Zhenghang Zhi, Hanzhi Ruan, Jiuming Liu, Xinpeng Li, Yong Zhang, Qi Yao, Chenjia Tang, Yujie Xiao, Xufeng Kou
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12219v1 Announce Type: new
Abstract: We report the epitaxial growth of high-quality Al0.8Ga0.2Sb-InAs-Al0.8Ga0.2Sb quantum well films featured by high carrier mobility and strong spin-orbit coupling. By appropriately optimizing the Al-to-Ga ratio in the AlGaSb barrier layer, the quantum confinement of the heterostructure is significantlyenhanced, which results in both an ultra-high electron mobility of 924000 cm2/Vs and a giant magnetoresistance ratio of 365000 at low temperatures. Meanwhile, pronounced Shubnikov-deHaas quantum oscillations persist up to 30 K, and their single-frequency feature indicates a well defined Fermi surface without subband mixing in the two-dimensional electron gas channel. Moreover, the large effective g-factor of 12.93 leads to the observation of Zeeman splitting at large magnetic fields. Our results validate the AlGaSb/InAs quantum well heterostructures as a suitable candidate for constructing energy-efficient topological spintronic devices.
Authors: Chaitanya B. Auti, Atul G. Chakkar, Shantanu Semwal, Sebastian Selter, Yuliia Shemerliuk, Bernd B\"uchner, Saicharan Aswartham, Koushik Pal, Pradeep Kumar
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12324v1 Announce Type: new
Abstract: Within the Landau theoretical framework, the decreased entropy with decreasing the temperature is accompanied by the symmetry breaking and hence a corresponding phase transition. The broken symmetries leave its imprint on the underlying excitations and the same may be gauged using renormalization of these excitations. AgCrP2S6 provides a versatile playground to probe dynamics of the quasiparticle excitations as well as multiple phase transitions with lowering temperature linked with the polar, lattice and spin degrees of freedom. Here, we report an in-depth temperature- and polarization-dependent Raman scattering measurements on single crystals of quasi 2D zigzag antiferromagnet AgCrP2S6 along with the first principle based phonon calculations. We observed multiple phase transitions triggered by the short and long-range ordering of spins at ~ 90 K and 20 K, respectively; within the Cr sublattice where spins are arranged in a 1D chain, evident by the distinct anomalies in the phonon modes self-energy parameters as well as intensity. Contrary to the conventional belief, we uncovered potential quasi-antipolar ordering at ~ 200 K and with further lowering in temperature an antipolar ordering at ~ 140 K attributed to the Ag ions, which is conjectured to be forbidden owing to the heaviness of Ag ions. The quasi-antipolar and antipolar ordering is gauged via the distinct renormalization of the phonon parameters, which survives at all the temperatures. Additionally, large number of modes appears with decreasing the temperature, in the window of ~ 200-140 K, where antipolar ordering starts settling in. The emergence of large number of phonon modes below ~ 200 K, nearly double of those at room temperature, suggests the lowering of symmetry from high temperature C2h to the low temperature C2 or Cs and as a result doubling of the unit cell.
Authors: Kai Liu, Yating Sha, Bo Yin, Shuhan Liu, Yulu Ren, Zhongxun Guo, Jingjing Gao, Ming Tian, Neng Wan, Kenji Watanabe, Takashi Taniguchi, Bingbing Tong, Guangtong Liu, Li Lu, Yuanbo Zhang, Weidong Luo, Zhiwen Shi, Quansheng Wu, Guorui Chen
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12478v1 Announce Type: new
Abstract: Graphene multilayers exhibit electronic spectra that depend sensitively on both the number of layers and their stacking order. Beyond trilayer graphene, mixed stacking sequences (alternating Bernal and rhombohedral layers) give rise to multiple coexisting low-energy bands. Here we investigate ABCBC-stacked pentalayer graphene, a less-studied non-centrosymmetric mixed sequence. This stacking can be regarded as an ABC (rhombohedral) trilayer on top of an AB (Bernal) bilayer, so its low-energy band structure contains both a cubic band and a parabolic band that hybridize. In transport measurements, we observe an intrinsic band gap at charge neutrality whose magnitude changes asymmetrically under an applied perpendicular displacement field. This behavior reflects the spontaneous layer polarization inherent to the broken inversion symmetry and mirror symmetry. By tuning the displacement field and carrier density, we drive multiple Lifshitz transitions in the Fermi surface topology and realize Landau levels with different degeneracies arising from the multi-flatband system. Remarkably, a v = -6 quantum Hall state emerges at an exceptionally low magnetic field (~20 mT), indicating the interplay between spontaneous symmetry breaking and Berry curvatures. Our results establish mixed-stacked multilayer graphene as a tunable platform with various broken symmetries and multiple flatbands, suitable for exploring emergent correlated electronic states.
Authors: Bo Hao, Maosen Wang, Wenjie Sun, Yang Yang, Zhangwen Mao, Shengjun Yan, Haoying Sun, Hongyi Zhang, Lu Han, Zhengbin Gu, Jian Zhou, Dianxiang Ji, Yuefeng Nie
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12603v1 Announce Type: new
Abstract: Recent studies have demonstrated ambient pressure superconductivity in compressively strained La$_{3}$Ni$_{2}$O$_{7}$ thin films, yet the phase diagram of heterovalent doping$-$critical for advancing the field$-$remains unexplored. Here, we report superconductivity in Sr$^{2+}$-doped La$_{3-x}$Sr$_{x}$Ni$_2$O$_7$ films synthesized via molecular beam epitaxy with ozone-assisted post-annealing. The superconducting transition temperature ($T_{\mathrm{c}}$) follows an asymmetric dome-like profile, persisting across a wide doping range ($0 \leq x \leq 0.21$) before diminishing at $x \approx 0.38$. Optimally doped films ($x = 0.09$) achieve $T_{\mathrm{c}}$ of $\sim$ 42 K, with high critical current ($J_{\mathrm{c}} > 1.4$ $\mathrm{kA/cm^{2}}$ at 2 K) and upper critical fields ($\mu_{0}H_{\mathrm{c,\parallel}}(0)= 83.7$ $\mathrm{T}$, $\mu_{0}H_{\mathrm{c,\perp}}(0)= 110.3$ $\mathrm{T}$), comparable to reported La$_{3-x}$Pr$_{x}$Ni$_2$O$_7$ films. Scanning transmission electron microscopy reveals oxygen vacancies predominantly occupy at planar NiO$_{2}$ sites$-$unlike apical-site vacancies in bulk samples$-$due to Coulomb repulsion destabilizing planar oxygen under compressive strain. Additionally, the elongated out-of-plane Ni-O bonds, exceeding those in pressurized bulk samples by $4\%$, likely weaken the interlayer $d_{z^2}$ coupling, thus contributing to the reduced $T_{\mathrm{c}}$ in strained films. This work establishes heterovalent Sr$^{2+}$ doping as a robust tuning parameter for nickelate superconductivity, unveiling a unique phase diagram topology.
Authors: Zhi-Ming Yang, Huan Li
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12673v1 Announce Type: new
Abstract: Nonsymmorphic symmetries can give rise to Dirac semimetal (DSM) states. However, few studies have been conducted on DSMs in interacting systems. Here, we induce interacting DSM states in nonsymmorphic iridium oxides SrIrO$_3$, BaIrO$_3$ and CaIrO$_3$, and contend that the interaction of electron-electron correlations, strong spin-orbital coupling, and symmetry protection can drive robust and exotic DSM states. Based on the density functional theory combined with dynamical mean-field theory (DFT + DMFT), with the Coulomb interaction parameters computed through doubly screened Coulomb correction approach, we discover that the Dirac fermions are constituted by the strongly spin-orbital coupled $J_{\mathrm{eff}} = 1/2$ states resulting from $t_{2g}$ orbits of Ir, with significant mass enhancement. Moreover, the nonsymmorphic symmetries induce topological surface bands and Fermi arcs on the (001) surface, which are well separated from bulk states. Our findings establish nonsymmorphic iridium oxides as correlated DSMs under strong electron-electron and spin-orbital interactions.
Authors: Xin-Wei Yi, Wei Li, Jing-Yang You, Bo Gu, Gang Su
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12733v1 Announce Type: new
Abstract: Recent strain-stabilized superconductivity at ambient pressure in La$_3$Ni$_2$O$_{7}$ films opens new avenues for nickelates research, in parallel with its pressure-induced counterpart. Using density functional theory calculations, we elucidate the critical factors bridging strain- and pressure-driven superconductivity in La$_3$Ni$_2$O$_{7}$ by comprehensively analyzing structural, electronic, magnetic, and density wave characteristics. Consistent with recent scanning transmission electron microscopy observations, we find an $I4/mmm$ structural transition at $-0.9\%$ strain, preceding superconductivity onset. Electronic analysis shows compressive strain lowers Ni-$d_{z^2}$ orbital energy levels, while interfacial Sr diffusion effectively reconstructs the $d_{z^2}$ pockets, quantitatively matching angle-resolved photoemission spectroscopy experiments. The interlayer antiferromagnetic coupling $J_\perp$ under pressure or strain closely tracks experimental superconducting $T_c$ variation. The dome-shaped pressure dependence and monotonic strain dependence of $J_\perp$ mainly arise from modulations in the apical oxygen $p_z$ energy levels. Moreover, compressive strain suppresses both charge density waves (CDW) and spin density waves (SDW) instabilities analogous to pressure effects, with SDW vanishing concurrently with the structural transition and CDW disappearing at $\sim-3.3\%$ strain. Our results indicate that suppressed density waves and enhanced $J_\perp$ are crucial for both strain- and pressure-driven superconductivity. Accordingly, we propose several candidate substrates capable of achieving greater compressive strain, thereby potentially increasing $T_c$.
Authors: Marios H. Michael, Gunda Kipp, Alexander M. Potts, Matthew W. Day, Toru Matsuyama, Guido Meier, Hope M. Bretscher, James W. McIver
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12799v1 Announce Type: new
Abstract: Two-dimensional materials and van der Waals (vdW) heterostructures host many strongly correlated and topological quantum phases on the $\sim$ meV energy scale. Direct electrodynamical signatures of such states are thus expected to appear in the terahertz (THz) frequency range (1 THz $\sim$ 4 meV). Because the typical size of vdW heterostructures ($\sim$10 $\mu m$) is much smaller than the diffraction limit of THz light, probing THz optical conductivities necessitates the use of near-field optical probes. However, interpreting the response of such near-field probes is complicated by finite-size effects, the presence of electrostatic gates, and the influence of the probe itself on material dynamics -- all of which conspire to form polaritonic self-cavities, in which interactions between THz electromagnetic fields and material excitations form discretized standing waves. In this paper, we demonstrate the relevance of self-cavity effects in 2D materials and derive an analytical framework to resolve these effects using the emerging experimental technique of time-domain on-chip THz spectroscopy. We show that by pairing experiments with the analytical theory, it is possible to extract the THz conductivity and resolve collective mode dynamics far outside the light cone, with $\sim \mu m$ in-plane and $\sim nm$ out-of-plane resolution. This study lays the groundwork for studying quantum phases and cavity effects in vdW heterostructures and 2D quantum materials.
Authors: Pal Jedlovszky, Christoph Dellago, Marcello Sega
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12953v1 Announce Type: new
Abstract: The discovery of high-density liquid (HDL) and low-density liquid (LDL) water has been a major success of molecular simulations, yet extending this analysis to interfacial water is challenging due to conventional order parameters assuming local homogeneity. This limitation previously prevented resolving the composition of the surface layer of the liquid/vapour interface. Here, we apply a recently introduced topological order parameter [R. Foffi and F. Sciortino, J. Phys. Chem. B 127, 378-386 (2022)] to analyze the composition of the water/vapor interface across a broad temperature range. Our results reveal that LDL-like water dominates the outermost region at all temperatures, while HDL-like water accumulates beneath it, presenting a clear layering roughly below the temperature of maximum density. This structured stratification, previously inaccessible, highlights the power of the topological order parameter in resolving interfacial molecular heterogeneity and provides new insights into the structural properties of water at interfaces.
Authors: Jean Spi\`ece, Roop Kumar Mech, Alessandra Canetta, Rebeca Ribeiro-Palau, Oleg Kolosov, Pascal Gehring
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12957v1 Announce Type: new
Abstract: Two-dimensional (2D) materials have attracted significant interest due to their tunable physical properties when stacked into heterostructures. Twisting adjacent layers introduces moire patterns that strongly influence the material's electronic and thermal behavior. In twisted graphene systems, the twist angle critically alters phonon transport, leading to reduced thermal conductivity compared to Bernal-stacked configurations. However, experimental investigations into thermal transport in twisted structures remain limited. Here, we study the local thermal properties of twisted double bilayer graphene (TDBG) using Scanning Thermal Microscopy (SThM). We find a reduction in thermal resistance of 0.3 +/- 0.1 x 10^6 K W^-1 compared to untwisted bilayers, attributed to changes in both intrinsic thermal conductivity and the tip-sample interface. These results, supported by analytical modeling, provide new insight into thermal transport mechanisms in twisted 2D systems and offer a pathway toward thermal engineering in twistronic devices.
Authors: David Immel, Matous Mrovec, Ralf Drautz, Godehard Sutmann
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12958v1 Announce Type: new
Abstract: We perform nanoindentation simulations for both the prototypical face-centered cubic metal copper and the body-centered cubic metal tungsten with a new adaptive-precision description of interaction potentials including different accuracy and computational costs: We combine both a computationally efficient embedded atom method (EAM) potential and a precise but computationally less efficient machine learning potential based on the atomic cluster expansion (ACE) into an adaptive-precision (AP) potential tailored for the nanoindentation. The numerically expensive ACE potential is employed selectively only in regions of the computational cell where large accuracy is required. The comparison with pure EAM and pure ACE simulations shows that for Cu, all potentials yield similar dislocation morphologies under the indenter with only small quantitative differences. In contrast, markedly different plasticity mechanisms are observed for W in simulations performed with the central-force EAM potential compared to results obtained using the ACE potential which is able to describe accurately the angular character of bonding in W due to its half-filled d-band. All ACE-specific mechanisms are reproduced in the AP nanoindentation simulations, however, with a significant speedup of 20-30 times compared to the pure ACE simulations. Hence, the AP potential overcomes the performance gap between the precise ACE and the fast EAM potential by combining the advantages of both potentials.
Authors: Yang Gao, Qi-Zheng Ji, Chao-Bo Liu, Qi Xiao, Chao Lian
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12989v1 Announce Type: new
Abstract: We employ real-time time-dependent density functional theory (RT-TDDFT) to investigate the electron-phonon-spin correlated dynamics in negatively charged nitrogen-vacancy centers (NV$^{-}$) and construct a comprehensive dynamical picture. Laser excitation promotes minority-spin electrons within 100~fs, establishing a three-fold rotation symmetry breaking (3RSB) charge ordering. Subsequently, ionic motion on the potential energy surface of the excited electrons generates two distinct dynamical modes: (1) symmetric oscillations of carbon-nitrogen bonds and (2) dynamic Jahn-Teller distortions (DJT) with 3RSB. These distortions induce nonlocal coherent phonons in the diamond lattice, which propagate with 3RSB at the sound velocity ($\sim$2~\AA/fs). Furthermore, the NV$^{-}$ spin state remains preserved during photoexcitation but undergoes rapid reorientation within 100~fs via enhanced spin-orbit-phonon coupling. Our RT-TDDFT simulations provide direct time-resolved visualization of these processes, offering novel insights into the microscopic interplay of electrons, phonons, and spins in NV$^{-}$ centers. These results advance the fundamental understanding of dynamical mechanisms in solid-state quantum systems, with implications for optimizing NV$^{-}$-based quantum sensing technologies.
Authors: N. V. Antonov, P. I. Kakin, N. M. Lebedev, A. Yu. Luchin
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13040v1 Announce Type: new
Abstract: We study a strongly anisotropic self-organized critical system coupled to an isotropic random fluid environment. The former is described by a continuous (coarse-grained) model due to Hwa and Kardar. The latter is modeled by the Navier--Stokes equation with a random stirring force of a rather general form that includes, in particular, the overall shaking of the system and a non-local part with power-law spectrum $\sim k^{4-d-y}$ that describes, in the limiting case $y \to 4$, a turbulent fluid. The full problem of the two coupled stochastic equations is represented as a field theoretic model which is shown to be multiplicatively renormalizable and logarithmic at $d=4$. Due to the interplay between isotropic and anisotropic interactions, the corresponding renormalization group (RG) equations reveal a rich pattern of possible infrared (large scales, long times) regimes of asymptotic behaviour of various Green's functions. The attractors of the RG equations in the five-dimensional space of coupling parameters include a two-dimensional surface of Gaussian (free) fixed points, a single fixed point that corresponds to the plain advection by the turbulent fluid (the Hwa--Kardar self-interaction is irrelevant) and a one-dimensional curve of fixed points that corresponds to the case where the Hwa--Kardar nonlinearity and the uniform stirring are simultaneously relevant. The character of attractiveness is determined by the exponent $y$ and the dimension of space $d$; the most interesting case $d=3$ and $y \to 4$ is described by the single fixed point. The corresponding critical dimensions of the frequency and the basic fields are found exactly.
Authors: Manuel Siegl, Julian Zanon, Joseph Sink, Adonai Rodrigues da Cruz, Holly Hedgeland, Neil J. Curson, Michael E. Flatt\'e, Steven R. Schofield
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13041v1 Announce Type: new
Abstract: We present the first scanning tunneling microscopy (STM) images of hydrogenic acceptor wave functions in silicon. These acceptor states appear as square ring-like features in STM images and originate from near-surface defects introduced by high-energy bismuth implantation into a silicon (001) wafer. Scanning tunneling spectroscopy confirms the formation of a p-type surface. Effective-mass and tight-binding calculations provide an excellent description of the observed square ring-like features, confirming their acceptor character and attributing their symmetry to the light- and heavy-hole band degeneracy in silicon. Detailed understanding of the energetic and spatial properties of acceptor wave functions in silicon is essential for engineering large-scale acceptor-based quantum devices.
Authors: Xiaoyu Cheng, Tiantao Qu, Yaqing Yang, Lei Zhang, Jun Chen
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13057v1 Announce Type: new
Abstract: Exceptional point (EP) and topological phase transition (TPT) in non-Hermitian systems have recently garnered significant attention owing to their fundamental importance and potential applications in sensing and topological devices. Beyond the EP induced by non-reciprocal hopping, we show that random disorder can also drive the valence and conduction bands across EPs, even twice in the non-Hermitian regime. Remarkably, a TPT can occur concurrently with an EP as disorder strength increases. These disorder-driven EPs and concurrent TPTs are well captured by effective medium theory. The analysis reveals that their emergence results from the interplay between disorder-induced energy level renormalization and non-reciprocal hopping-induced inter-level coupling, which fundamentally restructures the spectral properties of the system. The phase diagram in the parameter space of non-reciprocal hopping and disorder strength identifies robust EP lines. Interestingly, two EP lines can emerge from the TPT point in the Hermitian limit. As non-reciprocal hopping increases, these lines split, with one aligning the TPT, leading to distinct disorder-induced EPs. Our results uncover a robust, disorder-driven mechanism for generating EPs and concurrent TPTs, offering a new direction for exploring non-Hermitian topological matter.
Authors: Yuma Hirobe, Taisei Kitamura, Youichi Yanase
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13065v1 Announce Type: new
Abstract: The symmetry of Cooper pairs encodes key information about superconductivity and has been widely studied through the temperature dependence of the superfluid weight. However, in systems dominated by quantum geometry, conventional theories miss its essential properties. We study the temperature dependence of the quantum-geometric superfluid weight and classify the relationship to the superconducting symmetry and band structures. The obtained power laws are different from conventional behavior, and unconventional superconductivity in twisted multilayer graphene is discussed. Our findings provide insights into the superconducting symmetry and the pairing mechanism via quantum geometry.
Authors: Gabriel Elyas Gama Araujo, Andreia Luisa da Rosa, Alexandre Cavalheiro Dias, Thomas Frauenheim
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13107v1 Announce Type: new
Abstract: In this work we use first principles density-functional theory and Bethe-Salpeter equation together with tight-binding based maximally localized wannier functions (MLWF-TB) to investigate the electronic, optical and topological properties of two-dimensional bismuth (bismuthene) containing vacancy defects. We demonstrate that these properties depends on the shape and size of the nanopores. Furthermore, \textit{ab initio} molecular dynamics (AIMD) simulations shows that all pores are thermally stable at room temperature. Finally, adsorption of gas phase small molecules indicates that these pores can serve as sensors, opening the path for further applications in gas separation and sensing.
Authors: Gianmichele Blasi, Ricard Ravell Rodr\'iguez, Mykhailo Moskalets, Rosa L\'opez, G\'eraldine Haack
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13200v1 Announce Type: new
Abstract: Kinetic Uncertainty Relations (KURs) establish quantum transport precision limits by linking signal-to-noise ratio (SNR) to the system's dynamical activity, valid in the weak-coupling regime where particle-like transport dominates. At strong coupling, quantum coherence challenges the validity of KURs and questions the meaning of the concept of activity itself. Here, we introduce a generalized dynamical activity valid at arbitrary coupling and derive a steady-state quantum KUR (QKUR) expressed in terms of this generalized activity. Explicit expressions are obtained within Green's function and Landauer-B\"uttiker formalisms. This QKUR ensures that uncertainty relations are valid across all coupling strengths, offering a general framework for out-of-equilibrium quantum transport precision analysis. We illustrate these concepts for paradigmatic quantum-coherent mesoscopic devices: a single quantum channel pinched by a quantum point contact and open single- and double-quantum dot systems.
Authors: Hector Roche Carrasco, Justin Schirmann, Aurelien Mordret, Adolfo G. Grushin
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13304v1 Announce Type: new
Abstract: The strict geometric rules that define aperiodic tilings lead to the unique spectral and transport properties of quasicrystals, but also limit our ability to design them. In this work, we explore the first continuously tunable family of two-dimensional aperiodic tilings in which the underlying real-space geometry becomes a control knob of the wave-function's quantum geometric tensor. The real-space geometry can be used to tune into topological phases occupying an expanded phase space compared to crystals, or into a disorder-driven topological Anderson insulator. The quantum metric can also be tuned continuously, opening new routes towards tunable single- and many-body physics in aperiodic solid-state and synthetic systems.
Authors: Bruce D. Popp
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12168v1 Announce Type: cross
Abstract: This paper reviews a paper from 1906 by J. Henri Poincar\'e on statistical mechanics with a background in his earlier work and notable connections to J. Willard Gibbs. Poincar\'e's paper presents important ideas that are still relevant for understanding the need for probability in statistical mechanics. Poincar\'e understands the foundations of statistical mechanics as a many-body problem in analytical mechanics (reflecting his 1890 monograph on The Three-Body Problem and the Equations of Dynamics) and possibly influenced by Gibbs independent development published in chapters in his 1902 book, Elementary Principles in Statistical Mechanics. This dynamical systems approach of Poincar\'e and Gibbs provides great flexibility including applications to many systems besides gasses. This foundation benefits from close connections to Poincar\'e's earlier work. Notably, Poincar\'e had shown (e.g. in his study of non-linear oscillators) that Hamiltonian dynamical systems display sensitivity to initial conditions separating stable and unstable trajectories. In the first context it precludes proving the stability of orbits in the solar system, here it compels the use of ensembles of systems for which the probability is ontic and frequentist and does not have an a priori value. Poincar\'e's key concepts relating to uncertain initial conditions, and fine- and coarse-grained entropy are presented for the readers' consideration. Poincar\'e and Gibbs clearly both wanted to say something about irreversibility, but came up short.
Authors: Mehran Z-Abyaneh
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.12498v1 Announce Type: cross
Abstract: Using the doubled representation of Dirac spinors, we write the Lagrangian of a time-reversal symmetry broken three dimensional Weyl superconductor in a covariant form . Then, based on an analogy with the Nambu Jona-Lasinio model and by employing the Fierz transformations, we demonstrate that new collective modes should exist in such a system, including a pseudo-scalar Nambu-Goldstone boson and its corresponding amplitude mode plus a vector and an axial-vector collective mode. It is also observed that the pseudo-scalar mode can become massive due to an explicit chiral symmetry breaking term in the Lagrangian.
Authors: Francesco D'Amico, Dario Bocchi, Matteo Negri
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.13230v1 Announce Type: cross
Abstract: Scaling laws in deep learning - empirical power-law relationships linking model performance to resource growth - have emerged as simple yet striking regularities across architectures, datasets, and tasks. These laws are particularly impactful in guiding the design of state-of-the-art models, since they quantify the benefits of increasing data or model size, and hint at the foundations of interpretability in machine learning. However, most studies focus on asymptotic behavior at the end of training or on the optimal training time given the model size. In this work, we uncover a richer picture by analyzing the entire training dynamics through the lens of spectral complexity norms. We identify two novel dynamical scaling laws that govern how performance evolves during training. These laws together recover the well-known test error scaling at convergence, offering a mechanistic explanation of generalization emergence. Our findings are consistent across CNNs, ResNets, and Vision Transformers trained on MNIST, CIFAR-10 and CIFAR-100. Furthermore, we provide analytical support using a solvable model: a single-layer perceptron trained with binary cross-entropy. In this setting, we show that the growth of spectral complexity driven by the implicit bias mirrors the generalization behavior observed at fixed norm, allowing us to connect the performance dynamics to classical learning rules in the perceptron.
Authors: Pamela C. Guruciaga, Takafumi Ichikawa, Steffen Plunder, Takashi Hiiragi, Anna Erzberger
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2403.08710v3 Announce Type: replace
Abstract: Topological defects determine the collective properties of anisotropic materials. How their configurations are controlled is not well understood however, especially in 3D. In living matter moreover, 2D defects have been linked to biological functions, but the role of 3D polar defects is unclear. Combining computational and experimental approaches, we investigate how confinement geometry controls surface-aligned polar fluids, and what biological role 3D polar defects play in tissues interacting with extracellular boundaries. We discover a charge-preserving transition between 3D defect configurations driven by boundary geometry and independent of material parameters, and show that defect positions predict the locations where fluid-filled lumina -- structures essential for development -- form within the confined polar tissue of the mouse embryo. Experimentally perturbing embryo shape beyond the transition point, we moreover create additional lumina at predicted defect locations. Our work reveals how boundary geometry controls polar defects, and how embryos use this mechanism for shape-dependent lumen formation. We expect this defect control principle to apply broadly to systems with orientational order.
Authors: Yue Tang, Tiancheng Song, Haosen Guan, Yanyu Jia, Guo Yu, Zhaoyi Joy Zheng, Ayelet J. Uzan, Michael Onyszczak, Ratnadwip Singha, Xin Gui, Kenji Watanabe, Takashi Taniguchi, Robert J. Cava, Leslie M. Schoop, N. P. Ong, Sanfeng Wu
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2405.09665v2 Announce Type: replace
Abstract: The detection of Landau-level-like energy structures near the chemical potential of an insulator is essential to the search for a class of correlated electronic matter hosting charge-neutral fermions and Fermi surfaces, a long-proposed concept that remains elusive experimentally. Here we introduce and demonstrate that the magneto-thermoelectric response of a quantum insulator can reveal critical information not available via other approaches. We report the observation of large Seebeck response together with quantum oscillations (QOs) in the hole-doped insulating state of monolayer tungsten ditelluride (WTe2) in magnetic fields. The measured low temperature magneto-thermopower exceeds k_B/e by more than an order of magnitude, where k_B is the Boltzmann constant and e the elementary charge. This large thermopower is a characteristic of an insulating state, consistent with high resistivity. However, as the magnetic field is swept, QOs develop in the thermopower, which remarkably undergoes sign-changes that mimic the quantum characteristic of metals due to Landau quantization. The sign-change in the thermoelectric response directly implies the presence of a field-induced Landau-level-like structure at the chemical potential of the insulator. Neither the large thermopower nor the sign-changes can be induced by the metallic gate nearby. Our results demonstrate a new dilemma for investigating low energy excitations in correlated materials featuring mixed quantum characteristics of metals and insulators.
Authors: P. Sidorczak, W. Wo{\l}kanowicz, A. Kaleta, M. W\'ojcik, S. Giera{\l}towska, K. Gas, T. P{\l}oci\'nski, R. Minikayev, S. Kret, M. Sawicki, T. Wojtowicz, D. Wasik, M. Gryglas-Borysiewicz, K. Dybko
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2406.04447v3 Announce Type: replace
Abstract: This paper explores the potential for spin-triplet superconductivity in molecular beam epitaxy grown PbTe/SnTe semiconductor heterostructures. We present convincing evidence for spin-triplet pairing by soft point-contact spectroscopy experiments, using both spin-polarized and unpolarized electrons and additionally, by detailed analysis of the upper critical field, as inferred from the four probe resistance measurements. The experimental data are described in terms of the Anderson-Brinkman-Morel model of p-wave electron pairing. Our results confirm the predictions on strain-induced topological superconductivity by E.Tang and L. Fu (Nature Physics, 10, 964, 2014).
Authors: Arkady Kurnosov, Vassiliy Lubchenko
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2407.04829v3 Announce Type: replace
Abstract: We argue that the dominant charge carrier in glassy semiconducting alloys is a compound particle in the form of an electron or hole bound to an intimate pair of topological lattice defects; the particle is similar to the polaron solution of the Su-Schrieffer-Heeger Hamiltonian. The spatial component of the density of states for these special polarons is determined by the length scale of spatial modulation of electronegativity caused by a separate set of standalone topological defects. The latter length scale is fixed by the cooperativity size for structural relaxation; the size is largely independent of temperature in the glass but above melting, it decreases with temperature. Thus we predict that the temperature dependence of the electrical conductivity should exhibit a jump in the slope near the glass transition; the size of the jump is predicted to increase with the fragility of the melt. The predicted values of the jump and of the conductivity itself are consistent with experiment.
Authors: Xun-Jiang Luo, Jia-Zheng Li, Meng Xiao, Fengcheng Wu
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2407.20334v2 Announce Type: replace
Abstract: The abundance of bulk and boundary topologies in higher-order topological phases offer remarkable tunability and diversity to boundary states but also pose a challenge to their unified topological characterization. In this work, we propose a theoretical framework to characterize time-reversal invariant topological superconductors hosting Majorana Kramers pairs (MKP) of corner states by using a series of spin Bott indices, which capture both bulk and boundary states topology. The developed invariants can characterize MKP in arbitrarily shaped systems and all distinct spatial distribution patterns of MKP. As an illustrative example, we apply our theory to analyze the Kane-Mele model with sublattice-dependent superconducting pairing potentials. In this representative model, both intrinsic and extrinsic higher-order topological superconductors can be realized and various patterns of MKP can be engineered through edge cleavage. Despite their high sensitivity to boundary terminations, MKP can be faithfully characterized by the proposed topological invariants.We further demonstrate the characterization of higher-order topological superconductors in the BDI symmetry class using Bott indices without resolving the spin degree of freedom.
Authors: Yang-Zhi Chou, Jihang Zhu, Sankar Das Sarma
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2409.06701v2 Announce Type: replace
Abstract: We study the intravalley spin-polarized superconductivity in rhombohedral tetralayer graphene, which has been discovered experimentally in Han $et$ $al$ arXiv:2408.15233. We construct a minimal model for the intravalley spin-polarized superconductivity, assuming a simplified anisotropic interaction that depends only on the angle between the incoming and outgoing momenta. Despite the absence of \textit{Fermi surface nesting}, we show that superconductivity can emerge near the Van Hove singularity with the maximal $T_c$ near a bifurcation point of the peaks in the density of states. We identify the $p+ip$, $h+ih$, and the nodal $f$-wave pairings as the possible states, which are all pair density wave orders due to the intravalley nature. Furthermore, these pair density wave orders require a finite attractive threshold for superconductivity, resulting in {a narrow stripe shape of superconducting region}, consistent with experimental findings. We point out that the Kohn-Luttinger mechanism is a plausible explanation with a dominant $p+ip$ pairing. The possibility of realizing intravalley spin-polarized superconductivity in other rhombohedral graphene systems is also discussed.
Authors: Timo Schorlepp, Ohad Shpielberg
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2410.16043v3 Announce Type: replace
Abstract: Dynamical phase transitions are nonequilibrium counterparts of thermodynamic phase transitions and share many similarities with their equilibrium analogs. In continuous phase transitions, critical exponents play a key role in characterizing the physics near criticality. This study aims to systematically analyze the set of possible critical exponents in weak noise statistical field theories in 1+1 dimensions, focusing on cases with a single fluctuating field. To achieve this, we develop and apply the Gaussian fluctuation method, avoiding reliance on constructing a Landau theory based on system symmetries. Our analysis reveals that the critical exponents can be categorized into a limited set of distinct cases, suggesting a constrained universality in weak noise-induced dynamical phase transitions. We illustrate our findings in two examples: short-time large deviations of the Kardar-Parisi-Zhang equation, and the weakly asymmetric exclusion process on a ring within the framework of the macroscopic fluctuation theory.
Authors: Yvan Castin (LKB)
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2410.20866v2 Announce Type: replace
Abstract: We review some unresolved theoretical issues in three-dimensional two-component Fermi gases, drawing on recent experiments on cold atoms in immaterial traps close to a magnetic Feshbach resonance. We distinguish successively (i) the open questions arising in the few-body problem with Wigner-Bethe-Peierls contact interactions - essentially the stability of the gas with respect to the Efimov effect and the calculation of the cluster (or virial) coefficients, (ii) those arising in the effective low-energy theory of Landau and Khalatnikov quantum hydrodynamics - essentially the damping of phonon modes and the coherence time of the condensate of pairs, and finally (iii) questions requiring a complete, microscopic solution of the many-body problem, such as the specific properties of the acoustic excitation branch (Goldstone) of the condensate of pairs, or its collective excitation branch (Higgs) in the broken-pair continuum.
Authors: A. V. Rozhkov, A. O. Sboychakov, A. L. Rakhmanov
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2411.01309v2 Announce Type: replace
Abstract: We apply SU(4)-symmetric model to examine possible ordered states in AB stacked bilayer graphene (AB-BLG). The Hamiltonian of the system possesses this symmetry under certain assumptions. In such a model the multicomponent order parameter can be presented as a $4\times4$ matrix $\hat{Q}$. Using a mean field approximation, we derive a self-consistency equation for $\hat{Q}$. Among possible solutions of the obtained equation there are anomalous quantum Hall states, spin, charge, spin-valley density waves, inter-layer excitonic phases and their combinations. We argue that the proposed approach is a useful tool for classification of the ordered states in AB-BLG. The ordered states of the SU(4)-symmetric model demonstrate extensive degeneracies. The degeneracies can be removed by taking into account the neglected non-SU(4)-symmetric terms, disorder, substrate, as well as other perturbations. The ordered states have varying sensitivity to these factors. This suggests that, for AB-BLG, a ground state ordering type is a non-universal property, susceptible to particulars of extrinsic conditions.
Authors: K. Dinar, J. Delgado-Notario, C. Bray, K. Maussang, E. Perez-Martin, B. Benhamou-Bui, C. Consejo, S. Ruffenach, S. S. Krishtopenko, L. Bonnet, M. Paillet, J. Torres, Y. M. Meziani, I. Rozhansky, B. Jouault, S. Nanot, F. Teppe
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2411.16328v2 Announce Type: replace
Abstract: It has recently been shown that Terahertz sensors can effectively detect the spin resonances of Dirac fermions in graphene. The associated photovoltaic measurement technique allows for the investigation of the intrinsic spin-orbit coupling in graphene as well as its topological properties from microwave to Terahertz frequencies. In this work, using graphene/MoS2-based Field-Effect Transistors, we observed a magnetic resonance photovoltage signal in the Gigahertz range that is independent of the gate bias. The dispersion of the associated spin-flip transitions remains intriguingly unaffected by the MoS2 layer. In parallel, the spin-related signal consistently appears as a drop in photovoltage, regardless of the signal's polarity or origin, whether it arises from plasma wave rectification or thermoelectric effects. This behavior is interpreted as a decrease in the system's spin polarization due to spin-dependent recombination or scattering of photocarriers. Understanding the various photovoltaic signals in highly sensitive Gigahertz/Terahertz sensors paves the way for exploring spin-dependent mechanisms in two-dimensional quantum materials, influenced by proximity effects such as spin-orbit coupling, topology, and magnetism.
Authors: Ke Ding, Hao-Ran Zhang, Bai-Ting Liu, Shuo Yang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2412.07563v2 Announce Type: replace
Abstract: We generalize the topological response theory to detect the boundary anomalies of linear subsystem symmetries. This approach allows us to distinguish different subsystem symmetry-protected topological (SSPT) phases and uncover new ones. We focus on the cases where the mixed anomaly exists within the adjacent subsystems. Using numerical simulations, we demonstrate the power of this method by identifying strong and weak $Z_2^\tau\times Z_2^\sigma$ SSPT phases in a tunable tensor network state. Our analysis reveals an intrinsic $Z_2$ SSPT phase characterized by its degenerate entanglement spectrum. Furthermore, we extend the anomaly indicator to mixed-state density matrices and show that quantum anomalies of subsystem symmetry can persist under both uniform and alternating disorders. This finding establishes a connection between boundary quantum anomalies in pure and mixed states. Our work provides a numerical method to detect quantum anomalies of subsystem symmetries, offering new insights into the study of topological quantum phases.
Authors: Francisco Lobo, Elsa Prada, Pablo San-Jose
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2412.15174v2 Announce Type: replace
Abstract: Predictions of topological p-wave superconductivity and Majorana zero modes (MZMs) in hybrid superconductor-semiconductor nanowires have been difficult to realize experimentally. Consequently, researchers are actively exploring alternative platforms for MZMs. In this work, we theoretically study depleted nanowires with intrinsic superconductivity (as opposed to proximity-induced). Using a self-consistent Hartree-Fock-Bogoliubov mean field theory, we compute the topological phase diagram versus Zeeman field and filling for intrinsic wires with attractive interactions. We find that, although intrinsic wires could be less vulnerable than hybrids to topology-adverse effects, such as disorder and metallization, they are hindered by a fundamental limitation of their own. Although a topological p-wave gap is indeed possible, it is far less robust than in hybrid Majorana nanowires. Instead of remaining stable beyond the topological transition, it is found to decay exponentially with Zeema field, greatly reducing the parameter region with an appreciable topological gap.
Authors: Kevin Loo, Qing-Rui Wang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2412.18528v2 Announce Type: replace
Abstract: We use the pullback trivialization technique to systematically construct gapped interfaces and anomalous boundaries for fermionic symmetry-protected topological (FSPT) states by extending their symmetry group $G_f = \mathbb{Z}_2^f \times_{\omega_2} G$ to larger groups. These FSPT states may involve decoration layers of both Majorana chains and complex fermions. We derive general consistency formulas explicitly for (2+1)D and (3+1)D systems, where nontrivial twists arise from fermionic symmetric local unitaries or "gauge transformations" that ensure coboundaries vanish at the cochain level. Additionally, we present explicit example for a (3+1)D FSPT of symmetry group $G_f=\mathbb{Z}_2^f \times \mathbb{Z}_4 \times \mathbb{Z}_4$ with Majorana chain decorations.
Authors: M. Selch, M. A. Zubkov
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.00151v3 Announce Type: replace
Abstract: We consider macroscopic motion of $^3$He-A in global thermodynamic equilibrium within the context of the Zubarev statistical operator method. We formulate the corresponding effective theory in the language of the functional integral. The effective Lagrangian comprising macroscopic motion of fermionic excitations is calculated explicitly for the emergent relativistic fermions of the superfluid $^3$He-A-phase in the non-trivial bosonic background due to a space and time dependent matrix-valued vierbein featuring nonzero torsion as well as the Nieh-Yan anomaly. The matrix-valued vierbein formulation comprises an additional two dimensional internal spin space which may be replaced by one featuring a fermionic theory with a real valued vierbein, two Abelian gauge fields and a spin connection mixing the Dirac and internal spin spaces. As an application of the developed theory we consider macroscopic rotation around the axis of the pure integer mass vortices. The corresponding thermodynamical quantities of the normal component are analysed.
Authors: Konstantin L. Metlov
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.05290v2 Announce Type: replace
Abstract: Magnetic hopfions are three-dimensional topological solitons with non-zero Hopf index ${\cal H}$ in the vector field of material's local magnetization. In this Letter elliptical stability of hopfions with ${\cal H}=1$ in a classical helimagnet is studied on the basis of a variational model. It is shown that, depending on their internal structure (vortex and antivortex tubes ordering), the hopfions can either be stable in a bulk magnet or unstable with respect to elongation along their central axis. It is found that the energy of stable hopfions is always below the energy of the $2\pi$-skyrmion lattice in the same material, suggesting the possibility to use $2\pi$-skyrmions as a precursor for hopfion nucleation. Stability diagram for hopfions on the magnetic anisotropy-field phase diagram is computed numerically. Explicit analytical expressions for some of its critical lines are derived.
Authors: Ling-Na Wu, Xikun Li, Nathan Goldman, Botao Wang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.10720v3 Announce Type: replace
Abstract: Preparing fractional quantum Hall (FQH) states represents a key challenge for quantum simulators. While small Laughlin-type states have been realized by manipulating two atoms or two photons, scaling up these settings to larger ensembles stands as an impractical task using existing methods and protocols. In this work, we propose to use optimal-control methods to substantially accelerate the preparation of small Laughlin-type states, and demonstrate that the resulting protocols are also well suited to realize larger FQH states under realistic preparation times. Our schemes are specifically built on the recent optical-lattice experiment [Leonard et al., Nature (2023)], and consist in optimizing very few control parameters: the tunneling amplitudes and linear gradients along the two directions of the lattice. We demonstrate the robustness of our optimal-control schemes against control errors and disorder, and discuss their advantages over existing preparation methods. Our work paves the way to the efficient realization of strongly-correlated topological states in quantum-engineered systems.
Authors: Alejandro Simon, Reed Foster, Mihir Sahoo, James Shi, Emma Batson, Francesca Incalza, Matteo Castellani, Owen Medeiros, Christoph Heil, Karl K. Berggren
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.13791v3 Announce Type: replace
Abstract: Nonequilibrium quasiparticle (QP) and phonon dynamics are central to the operation of superconducting devices. Superconducting detectors, such as the superconducting nanowire single-photon detector, perform best when a large QP population is generated in response to small perturbations. Conversely, for superconducting qubits and topologically protected Majorana fermions, even relatively small QP densities can lead to significant performance degradation, and thus, ideal materials are less susceptible to QP poisoning. However, existing models of these devices lack a rigorous description of the QP and phonon dynamics, relying on approximations and phenomenology. In this article, we combine kinetic equations with density functional theory to model the nonequilibrium dynamics of a superconducting film ab initio. To demonstrate the universality of our model, we illustrate two examples: (1) we develop a model for the detection of single photons in superconducting nanowires, and (2) we calculate the energy-relaxation rate of a transmon qubit due to the presence of excess QPs. Our examples demonstrate from first principles that NbN is well-suited for single-photon detection and that Ta transmon qubits possess reduced sensitivity to QP poisoning relative to other materials, which is likely in part responsible for their longer coherence times. In contrast to previous models, our ab initio approach makes these predictions without experimental input and thus can be used to accelerate progress in device development. Moreover, by considering the full-bandwidth electron-phonon coupling, our approach can incorporate strong-coupling effects. Our methods effectively integrate ab initio materials modeling with nonequilibrium theory of superconductivity to perform practical modeling of superconducting devices, providing a comprehensive approach that connects fundamental theory with device applications.
Authors: Jing-Yu Zhao, Boran Zhou, Ya-Hui Zhang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2502.17430v3 Announce Type: replace
Abstract: The recent experimental studies of twisted bilayer graphene (TBG) raise a fundamental question: how do we understand Mott localization in a topological band? In this work, we offer a new perspective of Mott physics, which can be generalized to TBG directly in momentum space. In our theory, the Mott gap is understood as from an exciton-like hybridization $\Phi(\mathbf k) c^\dagger(\mathbf k)\psi(\mathbf k)$ between the physical electron $c$ and an ancilla fermion $\psi$. In the conventional Mott insulator of trivial band, the hybridization is $s$-wave with $\Phi(\mathbf k)=\frac{U}{2}$, where $U$ is the on-site Hubbard interaction. On the other hand, the band topology in TBG enforces a topological Mott hybridization with $\Phi(\mathbf k)\sim k_x \pm i k_y$ in a small region around $\mathbf{k}=0$. We dub this new Mott state as topological Mott localization because of the $p\pm ip$ order parameter analogous to the topological superconductor. At $\nu=0$, we find a topological Mott semimetal with a low energy effective theory resembling that of the untwisted bilayer graphene. For $\nu=\pm 1, \pm 2, \pm 3$, we show transitions from correlated insulators to Mott semimetals at smaller $U$. In the most intriguing density region $\nu=-2-x$, we propose a symmetric pseudogap metal at small $x$, which hosts a small Fermi surface and violates the perturbative Luttinger theorem. Interestingly, the quasiparticle is primarily formed by ancilla fermion, which we interpret as a composite fermion formed by a hole bound to a particle-hole pair. Our theory offers a unified language to describe the Mott localization in both trivial and topological bands in momentum space, and we anticipate applications in other moir\'e systems with topological Wannier obstruction, such as the twisted transition-metal dichalcogenide (TMD) homobilayer.
Authors: Steven Louis, Hannah Bradley, Artem Litvinenko, Vasyl Tyberkevych
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2503.20813v3 Announce Type: replace
Abstract: This work presents an equivalent circuit model for Magnetic Tunnel Junctions (MTJs) that accurately captures their magnetization dynamics and electrical behavior. Implemented in LTspice, the model is validated against direct numerical solutions of the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. It effectively simulates essential spintronic phenomena, including ferromagnetic resonance, field- and spin-torque-induced switching, and spin-torque-induced oscillations. Simulation results demonstrate strong agreement between LTspice and LLGS solutions, confirming the model accuracy and utility for efficient circuit-level analysis of spintronic devices. The ability to incorporate time-dependent magnetic fields and voltage inputs makes the proposed model suitable for diverse applications such as neuromorphic computing, microwave signal processing, and spintronic memory technologies. By providing a computationally efficient yet physically accurate circuit representation, this work enables seamless integration of MTJs into larger electronic systems, potentially accelerating the development of advanced spintronic circuit architectures.
Authors: G\"okhan \"Oztarhan, Pawe{\l} Potasz, A. D. G\"u\c{c}l\"u
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2504.01492v3 Announce Type: replace
Abstract: We present the emergence of Nagaoka ferromagnetism in semiconductor-based artificial graphene with realistic Coulomb interaction using high-precision variational and diffusion Monte Carlo methods, complemented by exact diagonalization calculations of the generalized Hubbard model. We analyze models of armchair hexagonal geometries nanopatterned on GaAs quantum wells. Our results reveal a distinct magnetic phase transition driven by the absence/addition of a single electron at half-filling. This form of itinerant magnetism predicted rigorously for Hubbard model remained unascertained in large scale realistic systems. We demonstrate that Coulomb scattering terms play a crucial role in stabilizing Nagaoka ferromagnetism, enabling the observation of the phase transition for system parameters near $U/t \approx 60$.
Authors: Jia-Xin Zhang, Wen O. Wang, Leon Balents, Lucile Savary
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2504.03882v2 Announce Type: replace
Abstract: The absence of a well-defined Fermi surface in flat-band systems challenges the conventional understanding of instabilities toward Landau order based on nesting. We investigate the existence of an intrinsic nesting structure encoded in the band geometry (i.e. the wavefunctions of the flat band(s)), which leads to a maximal susceptibility at the mean-field level and thus determines the instability towards ordered phases. More generally, we show that for a given band structure and observable, we can define two vector fields: one which corresponds to the Bloch vector of the projection operator onto the manifold of flat bands, and another which is "dressed" by the observable. The overlap between the two vector fields, possibly shifted by a momentum vector $\boldsymbol{Q}$, fully determines the mean field susceptibility of the corresponding order parameter. When the overlap is maximized, so is the susceptibility, and this geometrically corresponds to "perfect nesting" of the band structure. In that case, we show that the correlation length of this order parameter, even for $\boldsymbol{Q}\neq \boldsymbol{0}$, is entirely characterized by a generalized quantum metric in an intuitive manner, and is therefore lower-bounded in topologically non-trivial bands. As an example, we demonstrate hidden nesting for staggered antiferromagnetic spin order in an exactly flat-band model, which is notably different from the general intuition that flat bands are closely associated with ferromagnetism. We check the actual emergence of this long-range order using the determinantal quantum Monte Carlo algorithm. Additionally, we demonstrate that a Fulde-Ferrell-Larkin-Ovchinnikov-like state (pairing with non-zero center of mass momentum) can arise in flat bands upon breaking time-reversal symmetry, even if Zeeman splitting is absent.
Authors: Akimitsu Kirikoshi, Satoru Hayami
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2504.18093v2 Announce Type: replace
Abstract: A highly geometrically frustrated lattice structure such as a distorted kagome (or quasikagome) structure enriches physical phenomena through coupling with the electronic structure, topology, and magnetism. Recently, it has been reported that an intermetallic HoAgGe exhibits two distinct magnetic structures with the finite magnetic vector $q=(1/3,1/3,0)$: One is the partially ordered state in the intermediate-temperature region, and the other is the kagome spin ice state in the lowest-temperature region. We theoretically elucidate that the former is characterized by antiferrotoroidal ordering, while the latter is characterized by ferritoroidal ordering based on the multipole representation theory, which provides an opposite interpretation to previous studies. We also show how antiferrotoroidal and ferritoroidal orderings are microscopically formed by quantifying the magnetic toroidal moment activated in a multiorbital system. As a result, we find that the degree of distortion for the kagome structure plays a significant role in determining the nature of antiferrotoroidal and ferritoroidal orderings, which brings about the crossover between the antiferro-type and the ferri-type distributions of the magnetic toroidal dipole. We confirm such a tendency by evaluating the linear magnetoelectric effect. Our analysis can be applied irrespective of lattice structures and magnetic vectors without annoying the cluster origin.
Authors: Anas Abdelwahab
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2504.18228v4 Announce Type: replace
Abstract: The phase diagrams of arbitrary number $N_{\text{w}}$ of diagonally and perpendicularly coupled Su-Schrieffer-Heeger wires have been identified. The diagonally coupled wires have rich topological phase diagrams exhibiting insulating phases with winding numbers $0\leq w \leq N_{\text{w}}$ and topological critical lines restricted by the reflection mirror symmetry. Even number of perpendicularly coupled wires exhibit either gapless or trivial topological phases. Odd number of perpendicularly coupled wires additionally exhibit nontrivial topological phases with winding number $w=1$. Due to the mirror reflection symmetry, their gapless regions can be topologically nontrivial. They reveal coherent confined correlations in the odd indexed wires with strong wire-wire coupling away from the gapless regions.
Authors: Ting-Wei Hsu, Zhenyao Fang, Arun Bansil, Qimin Yan
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.04862v2 Announce Type: replace
Abstract: Optical spectra serve as a powerful tool for probing the interactions between materials and light, unveiling complex electronic structures such as flat bands and nontrivial topological features. These insights are crucial for the development and optimization of photonic devices, including solar cells, light-emitting diodes, and photodetectors, where understanding the electronic structure directly impacts device performance. Moreover, in anisotropic bulk materials, the optical responses are direction-dependent, and predicting those response tensors still remains computationally demanding due to its inherent complexity and the constraint from crystal symmetry. To address this challenge, we introduce the sequential tensorial properties equivariant neural network (StepENN), a graph neural network architecture that maps crystal structures directly to their full optical tensors across different photon frequencies. By encoding the isotropic sequential scalar components and anisotropic sequential tensor components into l=0 and l=2 spherical tensor components, StepENN ensures symmetry-aware sequential tensor predictions that are consistent with the inherent symmetry constraints of crystal systems. Trained on a dataset of frequency-dependent permittivity tensors for 1,432 bulk semiconductors computed from first-principles methods, our model achieves a mean absolute error (MAE) of 24.216 millifarads per meter (mF/m) on the predicted tensorial spectra with 85.7% of its predictions exhibiting less than 10% relative error, demonstrating its potential for deriving other spectrum-related properties, such as optical conductivity. This framework opens new avenues for the data-driven design of materials with engineered anisotropic optical responses, accelerating material advances in optoelectronic applications.
Authors: Shian Xia, Yan Luo, Iftikhar Ahmed Malik, Xinyi Zhou, Keying Han, Yue Sun, Haoyun Lin, Hanqing Shi, Yingchun Cheng, Vanessa Li Zhang, Yi Du, Sheng Liu, Chao Zhu, Ting Yu
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.06924v2 Announce Type: replace
Abstract: The emergence of two-dimensional (2D) van der Waals (vdW) ferromagnets has opened new avenues for exploring topological spin textures and their applications in next-generation spintronics. Among these materials, Fe3GaTe2 (FGaT) emerges as a model system due to its room-temperature skyrmion phases, which are stabilized by strong Dzyaloshinskii-Moriya interaction (DMI). However, the atomistic origins of DMI in centrosymmetric vdW lattices remain elusive. Here, we report a spontaneous DMI enhancement mechanism driven by FC in FGaT and its analog Fe3GeTe2 (FGeT). Combining Raman spectroscopy and scanning transmission electron microscopy (STEM), we have observed the irreversible precipitation of FeTe2 in annealed FGaT. The resulting FeTe2/FGaT heterostructure is considered to break the symmetry and significantly enhance the DMI. Furthermore, similar phenomenon has been observed in the family ferromagnetic material FGeT as well. Additionally, the precipitation of FeTe2 varies significantly with different thicknesses of FGaT, aligning closely with the reported behavior of skyrmions. This discovery provides new insights into the mechanisms behind the origin of the DMI in ternary tellurides, paving the way for advanced spintronic applications.
Authors: Afonso D. M. Barroso, Elijah Borodin, Andrey P. Jivkov
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.08689v3 Announce Type: replace
Abstract: Continuum models of plasticity fail to capture the richness of microstructural evolution because the continuum is a homogeneous construction. The present study shows that an alternative way is available at the mesoscale in the form of truly discrete constructions and in the discrete exterior calculus. A pre-existing continuum mean-field model with two parameters is rewritten in the language of the latter to model the properties of a network of plastic slip events in a perfect copper single crystal under uniaxial tension. The behaviour of the system is simulated in a triangular 2D mesh in 3D space employing a Metropolis-Hastings algorithm. Phases of distinct character emerge and both first-order and second-order phase transitions are observed. The phases represent arrangements of the plastic slip network with different combinations of collinear, coplanar, non-collinear and non-coplanar active slip systems. Furthermore, some of these phases can be interpreted as representing crystallographic phenomena like activation of secondary slip systems, strain localisation and fracture or amorphisation. The first-order transitions mostly occur as functions of the applied stress, while the second-order transitions occur exclusively as functions of the mean-field coupling parameter. The former are reminiscent of transitions in other statistical-mechanical models, while the latter find parallels in experimental observations.
Authors: Olha A. Kovalenko, Eugene A. Eliseev, Yuriy O. Zagorodniy, Sre\v{c}o Davor \v{S}kapin, Marjeta Ma\v{c}ek Kr\v{z}manc, Lesya Demchenko, Valentyn V. Laguta, Zdravko Kutnjak, Dean R. Evans, Anna N. Morozovska
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2505.09835v2 Announce Type: replace
Abstract: We investigate the impact of OH- ions incorporation on the lattice strain and spontaneous polarization of BaTiO3 nanorods synthesized under different conditions. It was confirmed that the lattice strain depends directly on Ba supersaturation, with higher supersaturation leading to an increase in the lattice strain. However, it was shown that crystal growth and observed lattice distortion are not primarily influenced by external strain; rather, OH- ions incorporation plays a key role in generating internal chemical strains and driving these processes. By using the less reactive TiO2 precursor instead of TiOCl2 and controlling Ba supersaturation, the slower nucleation rate enables more effective regulation of OH- ions incorporation and crystal growth. This in turn effects both particle size and lattice distortion, leading to c/a ratio of 1.013 - 1.014. The incorporation of OH- ions induces lattice elongation along the c-axis, contributing to anisotropic growth, increasing of the rod diameter and their growth-induced bending. However, the possibility of the curvature-induced changes in domain morphology of BaTiO3 nanorods remains almost unexplored. To study the possibility, we perform analytical calculations and finite element modeling, which provide insights into the curvature-induced changes in the strain-gradient, polarization distribution, and domain morphology in BaTiO3 nanorods. Theoretical results reveal the appearance of the domain stripes in BaTiO3 nanorod when the curvature exceeds a critical angle. The physical origin of the domain stripes emergence is the tendency to minimize its elastic energy of the nanorod by the domain splitting. These findings suggest that BaTiO3 nanorods, with curvature-controllable amount of domain stripes, could serve as flexible race-track memory elements for flexo-tronics and domain-wall electronics.
Authors: L. Marsot, P. -M. Zhang, M. Chernodub, P. A. Horvathy
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2212.02360v4 Announce Type: replace-cross
Abstract: ``Do Carroll particles move?'' The answer depends on the characteristics of the particle such as its mass, spin, electric charge, and magnetic moment. A massive Carroll particle (closely related to fractons) does not move; its immobility follows from Carroll boost symmetry which implies dipole conservation, but not conversely. A massless Carroll particle may propagate by following the Hall law, consistently with the partial breaking of the Carroll boost symmetry. The framework is extended to Carroll field theory. In $d=2$ space dimensions, the Carroll group has a two-fold central extension which allows us to generalize the dynamics to massive and massless particles, including anyons. The anyonic spin and magnetic moment combine with the doubly-extended structure parameterized by two Casimir invariants interpreted as intrinsic magnetization and non-commutativity parameter. The extended Carroll particle subjected to an electromagnetic background field moves following a generalized Hall law which includes a Zeeman force. This theory is illustrated by massless, uncharged anyons with doubly-centrally extended structure we call exotic photons, which move on the horizon of a Black Hole, giving rise to an anyonic spin-Hall Effect.
Authors: Christian Duval, Malte Henkel, Peter Horvathy, Shain Rouhani, Pengming Zhang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2403.20316v3 Announce Type: replace-cross
Abstract: This paper reviews the history of the conformal extension of Galilean symmetry, now called Schr\"odinger symmetry. In the physics literature, its discovery is commonly attributed to Jackiw, Niederer and Hagen (1972). However, Schr\"odinger symmetry has a much older ancestry: the associated conserved quantities were known to Jacobi in 1842/43 and its euclidean counterpart was discovered by Sophus Lie in 1881 in his studies of the heat equation. A convenient way to study Schr\"odinger symmetry is provided by a non-relativistic Kaluza-Klein-type "Bargmann" framework, first proposed by Eisenhart (1929), but then forgotten and re-discovered by Duval {\it et al.} only in 1984. Representations of Schr\"odinger symmetry differ by the value $z=2$ of the dynamical exponent from the value $z=1$ found in representations of relativistic conformal invariance. For generic values of $z$, whole families of new algebras exist, which for $z=2/\ell$ include the $\ell$-conformal galilean algebras. We also review the non-relativistic limit of conformal algebras and that this limit leads to the $1$-conformal galilean algebra and not to the Schr\"odinger algebra. The latter can be recovered in the Bargmann framework through reduction. A distinctive feature of Galilean and Schr\"odinger symmetries are the Bargmann super-selection rules, algebraically related to a central extension. An empirical consequence of this was known as "mass conservation" already to Lavoisier. As an illustration of these concepts, some applications to physical ageing in simple model systems are reviewed.
Authors: Yingjian Liu, Piotr Sierant, Paolo Stornati, Maciej Lewenstein, Marcin P{\l}odzie\'n
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2405.03338v2 Announce Type: replace-cross
Abstract: Inverse Participation Ratios (IPRs) and the related Participation Entropies quantify the spread of a quantum state over a selected basis of the Hilbert space, offering insights into the equilibrium and non-equilibrium properties of the system. In this work, we propose three quantum algorithms to estimate IPRs on multi-qubit and multi-qudit quantum devices. The first algorithm allows for the estimation of IPRs in the computational basis by single-qubit measurements, while the second one enables measurement of IPR in the eigenbasis of a selected Hamiltonian, without the knowledge about the eigenstates of the system. Next, we provide an algorithm for IPR in the computational basis for a multi-qudit system. We discuss resources required by the algorithms and benchmark them by investigating the one-axis twisting protocol, the thermalization in a deformed PXP model, and the ground state of a spin-$1$ AKLT chain in a transverse field.
Authors: Martin Ritter, David M. Long, Qianao Yue, Anushya Chandran, Alicia J. Koll\'ar
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2410.12908v2 Announce Type: replace-cross
Abstract: Floquet engineering, in which the properties of a quantum system are modified through the application of strong periodic drives, is an indispensable tool in atomic and condensed matter systems. However, it is inevitably limited by intrinsic heating processes. We describe a simple autonomous scheme, which exploits a static coupling between the driven system and a lossy auxiliary, to cool large classes of Floquet systems into desired states. We present experimental and theoretical evidence for the stabilization of a chosen quasienergy state in a strongly modulated transmon qubit coupled to an auxiliary microwave cavity with fixed frequency and photon loss. The scheme naturally extends to Floquet systems with multiple degrees of freedom. As an example, we demonstrate the stabilization of topological photon pumping in a driven cavity-QED system numerically. The coupling to the auxiliary cavity increases the average photon current and the fidelity of non-classical states, such as high photon number Fock states, that can be prepared in the system cavity.
Authors: Fuyang Tay, Stephen Sanders, Andrey Baydin, Zhigang Song, Davis M. Welakuh, Alessandro Alabastri, Vasil Rokaj, Ceren B. Dag, Junichiro Kono
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2410.21171v2 Announce Type: replace-cross
Abstract: Strong coupling between matter and vacuum electromagnetic fields in a cavity can induce novel quantum phases in thermal equilibrium via symmetry breaking. Particularly intriguing is the coupling with circularly polarized cavity fields, which can break time-reversal symmetry (TRS) and lead to topological bands. This has spurred significant interest in developing chiral cavities that feature broken TRS, especially in the terahertz (THz) frequency range, where various large-oscillator-strength resonances exist. Here, we present a design for high-quality-factor THz chiral photonic-crystal cavities (PCCs) that achieves broken TRS using a magnetoplasma in a lightly doped semiconductor. We incorporate ab initio density functional theory calculations into the derived microscopic model, allowing a realistic estimate of the vacuum-induced gap in graphene when coupled to our chiral cavity. Our calculations show an enhancement in the light-matter interaction due to Dirac nodes and predict an energy gap on the order of 1 meV. The THz chiral PCCs offer a promising platform for exploring cavity-dressed condensed matter with broken TRS.
Authors: Barak Gabai, Victor Gorbenko, Jiaxin Qiao, Bernardo Zan, Aleksandr Zhabin
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2410.24142v5 Announce Type: replace-cross
Abstract: We study quantum field theories which have quantum groups as global internal symmetries. We show that in such theories operators are generically non-local, and should be thought as living at the ends of topological lines. We describe the general constraints of the quantum group symmetry, given by Ward identities, that correlation functions of the theory should satisfy. We also show that generators of the symmetry can be represented by topological lines with some novel properties. We then discuss a particular example of $U_q(sl_2)$ symmetric CFT, which we solve using the bootstrap techniques and relying on the symmetry. We finally show strong evidence that for a special value of $q$ a subsector of this theory reproduces the fermionic formulation of the Ising model. This suggests that a quantum group can act on local operators as well, however, it generically transforms them into non-local ones.
Authors: Kaiyuan Cao, Tianren Zhang, Xiangping Jiang, Jian Wang
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.06794v3 Announce Type: replace-cross
Abstract: We investigate dynamical quantum phase transitions (DQPTs) in both pure and mixed states within the extended SSH model framework, focusing on the SSH-3 and SSH-4 variants, which differ in symmetry properties. The SSH-3 model, characterized by a chiral-like point symmetry rather than true chiral symmetry, supports robust localized edge states tied to its topological nature. Our results show that for pure states, DQPTs occur after quenches crossing the topological transition, even when the energy band gap remains open. For mixed states, DQPT behavior aligns with pure states at low temperatures but undergoes significant changes at higher temperatures, including the emergence of multiple critical times. In contrast, the SSH-4 model, which possesses chiral symmetry, features four distinct energy spectrum configurations. We find that pure-state DQPTs arise only when the quench starts from a gapless initial state and crosses the critical topological point. At finite temperature, mixed-state DQPTs persist at low temperatures only if the corresponding pure-state quench induces DQPTs, but they disappear at elevated temperatures. These findings elucidate the interplay between symmetry, topology, and temperature in governing DQPTs within generalized SSH models.
Authors: Kaito Takanami, Takashi Takahashi, Ayaka Sakata
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.16226v3 Announce Type: replace-cross
Abstract: Self-distillation (SD), a technique where a model improves itself using its own predictions, has attracted attention as a simple yet powerful approach in machine learning. Despite its widespread use, the mechanisms underlying its effectiveness remain unclear. In this study, we investigate the efficacy of hyperparameter-tuned multi-stage SD with a linear classifier for binary classification on noisy Gaussian mixture data. For the analysis, we employ the replica method from statistical physics. Our findings reveal that the primary driver of SD's performance improvement is denoising through hard pseudo-labels, with the most notable gains observed in moderately sized datasets. We also identify two practical heuristics to enhance SD: early stopping that limits the number of stages, which is broadly effective, and bias parameter fixing, which helps under label imbalance. To empirically validate our theoretical findings derived from our toy model, we conduct additional experiments on CIFAR-10 classification using pretrained ResNet backbone. These results provide both theoretical and practical insights, advancing our understanding and application of SD in noisy settings.
Authors: Martin Ritter, David M. Long, Qianao Yue, Maya Amouzegar, Anushya Chandran, Alicia J. Koll\'ar
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2501.17915v2 Announce Type: replace-cross
Abstract: Topological Floquet energy pumps -- which use periodic driving to create a topologically protected quantized energy current -- have been proposed and studied theoretically, but have never been observed directly. Previous work proposed that such a pump could be realized with a strongly-driven superconducting qubit coupled to a cavity. Here, we experimentally demonstrate that the proposed hierarchy of energy scales and drive frequencies can be realized using a transmon qubit. We develop an experimental toolkit to realize the adiabatic driving field required for energy pumping using coordinated frequency modulation of the transmon and amplitude modulation of an applied resonant microwave drive. With this toolkit, we measure adiabatic evolution of the qubit under the applied field for times comparable to $T_1$, which far exceed the bare qubit dephasing time. This result paves the way for direct experimental observation of topological energy pumping.
Authors: Dip Joti Paul, Tony X. Zhou, Karl K. Berggren
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2503.00169v2 Announce Type: replace-cross
Abstract: In this work, we present a technique to determine the mid-infrared refractive indices of thin superconducting films using Fourier transform infrared spectroscopy (FTIR). In particular, we performed FTIR transmission and reflection measurements on 10-nm-thick NbN and 15-nm-thick MoSi films in the wavelength range of 2.5 to 25 $\mu$m, corresponding to frequencies of 12-120 THz or photon energies of 50-500 meV. To extract the mid-infrared refractive indices of these thin films, we used the Drude-Lorentz oscillator model to represent their dielectric functions and implemented an optimization algorithm to fit the oscillator parameters by minimizing the error between the measured and simulated FTIR spectra. We performed Monte Carlo simulations in the optimization routine to estimate error ranges in the extracted refractive indices resulting from multiple sources of measurement uncertainty. To evaluate the consistency of the extracted dielectric functions, we compared the refractive indices extrapolated from these dielectric functions in the UV to near-infrared wavelengths with the values separately measured using spectroscopic ellipsometry. We validated the applicability of the extracted mid-infrared refractive indices of NbN and MoSi at temperatures below their critical temperatures by comparing them with the Mattis-Bardeen model. This FTIR-based refractive index measurement approach can be extended to measure the refractive indices of thin films at wavelengths beyond 25 $\mu$m, which will be useful for designing highly efficient photon detectors and photonic devices with enhanced optical absorption in the mid- and far-infrared wavelengths.
Authors: Zijian Liang, Ke Liu, Hao Song, Yu-An Chen
Published: Tue, 20 May 2025 00:00:00 -0400
arXiv:2503.03827v2 Announce Type: replace-cross
Abstract: The Kitaev toric code is widely considered one of the leading candidates for error correction in fault-tolerant quantum computation. However, direct methods to increase its logical dimensions, such as lattice surgery or introducing punctures, often incur prohibitive overheads. In this work, we introduce a ring-theoretic approach for efficiently analyzing topological CSS codes in two dimensions, enabling the exploration of generalized toric codes with larger logical dimensions on twisted tori. Using Gr\"obner bases, we simplify stabilizer syndromes to efficiently identify anyon excitations and their geometric periodicities, even under twisted periodic boundary conditions. Since the properties of the codes are determined by the anyons, this approach allows us to directly compute the logical dimensions without constructing large parity-check matrices. Our approach provides a unified method for finding new quantum error-correcting codes and exhibiting their underlying topological orders via the Laurent polynomial ring. This framework naturally applies to bivariate bicycle codes. For example, we construct optimal weight-6 generalized toric codes on twisted tori with parameters $[[ n, k, d ]]$ for $n \leq 400$, yielding novel codes such as $[[120,8,12]]$, $[[186,10,14]]$, $[[210,10,16]]$, $[[248, 10, 18]]$, $[[254, 14, 16]]$, $[[294, 10, 20]]$, $[[310, 10, \leq 22]]$, and $[[340, 16, 18]]$. Moreover, we present a new realization of the $[[360, 12, \leq 24]]$ quantum code using the $(3,3)$-bivariate bicycle code on a twisted torus defined by the basis vectors $(0,30)$ and $(6,6)$, improving stabilizer locality relative to the previous construction. These results highlight the power of the topological order perspective in advancing the design and theoretical understanding of quantum low-density parity-check (LDPC) codes.
Feed: Nature Nanotechnology
Authors: Jianhua Wu, Zhongxin Chen, Ke Yang, Xin Zhou, Huizhi Li, Zhiyong Wang, Mengyao Su, Rongrong Zhang, Tie Wang, Qikun Hu, Ning Yan, Cuibo Liu, Bin Zhang, Ming Yang, Shibo Xi, Kian Ping Loh
Published: 2025-05-19
Nature Nanotechnology, Published online: 19 May 2025; doi:10.1038/s41565-025-01934-z
A dynamic Cu–Pt dual-atom catalyst supported on 1Tʹ-MoS2 can be electrically switched between single- and dual-atom configurations, enabling on-demand control for alkyne semi-hydrogenation.
Feed: Nature Reviews Physics
Authors: Shaurya Aarav
Published: 2025-05-19
Nature Reviews Physics, Published online: 19 May 2025; doi:10.1038/s42254-025-00840-6
Shaurya Aarav introduces a quantum imaging method that uses a high-resolution camera to speed up imaging acquisition while retaining correlation information.
Authors: Marta Garcia-Gasulla, Mervi J. Mantsinen
Published: 2025-05-19
Nature Reviews Physics, Published online: 19 May 2025; doi:10.1038/s42254-025-00830-8
This Perspective provides a brief, opinionated review of the past, present and future of the convergence between supercomputing and fusion simulations. We discuss the progress that has been made, the challenges that have been overcome and those that remain as we move into the post-exascale era.
Authors: Ludovic Berthier, Giulio Biroli, Lisa Manning, Francesco Zamponi
Published: 2025-05-19
Nature Reviews Physics, Published online: 19 May 2025; doi:10.1038/s42254-025-00833-5
Amorphous materials yield through complex, history-dependent mechanisms involving localized defects and avalanche dynamics. This Review unifies theoretical advances across glasses, foams, biological tissues and active matter, revealing universal features and critical behaviour that govern the transition from elasticity to plastic flow and macroscopic failure.
Feed: Recent Articles in Phys. Rev. Lett.
Authors: Bikun Li, Zhaoyou Wang, Guo Zheng, Yat Wong, and Liang Jiang
Published: 2025-05-19T10:00:00+00:00
Author(s): Bikun Li, Zhaoyou Wang, Guo Zheng, Yat Wong, and Liang Jiang
In quantum error correction, the Petz map serves as a perfect recovery map when the Knill-Laflamme conditions are satisfied. Notably, while perfect recovery is generally infeasible for most quantum channels of finite dimension, the Petz map remains a versatile tool with near-optimal performance in r…
[Phys. Rev. Lett. 134, 200602] Published Mon May 19, 2025
Authors: Ruizhi Dong, Yihuan Zhu, Dongxing Mao, Xu Wang, and Yong Li
Published: 2025-05-19T10:00:00+00:00
Author(s): Ruizhi Dong, Yihuan Zhu, Dongxing Mao, Xu Wang, and Yong Li
Bound states in the continuum (BICs) are exceptional resonances with extremely high sensitivity and thus inherently fragile. Introducing topological concepts can fortify BICs against perturbations; however, existing topological BICs (TBICs) often rely on intricate strategies. Here, we explore the un…
[Phys. Rev. Lett. 134, 206601] Published Mon May 19, 2025
Feed: ACS Nano: Latest Articles (ACS Publications)
Authors: Yu Liu, Roger Proksch, Jason Bemis, Utkarsh Pratiush, Astita Dubey, Mahshid Ahmadi, Reece Emery, Philip D. Rack, Yu-Chen Liu, Jan-Chi Yang, and Sergei V. Kalinin
Published: Mon, 19 May 2025 04:38:37 PDT
ACS Nano
DOI: 10.1021/acsnano.4c18760
Authors: Rui Wang, Zishun Li, Shunyu Chang, Zihan Li, Yue Liu, Nan Qin, Wen-Zhu Shao, Cheng-Yan Xu, Liang Zhen, Tiger H. Tao, Yanquan Geng, Xiaorui Zheng, and Yang Li
Published: Mon, 19 May 2025 05:52:18 PDT
ACS Nano
DOI: 10.1021/acsnano.5c07017
Feed: Physical sciences : Nature Communications subject feeds
Authors: No author
Published: Mon, 19 May 2025 00:00:00 +0000
Authors: No author
Published: Mon, 19 May 2025 00:00:00 +0000
Authors: No author
Published: Mon, 19 May 2025 00:00:00 +0000
Feed: Wiley: Small: Table of Contents
Authors: Geon Woong Kim,
So Youn Kim
Published: Mon, 19 May 2025 00:46:38 -0700
Small, EarlyView.
Authors: Chao Zhang,
Kai Wu,
Luyan Wu,
Guoyang Cao,
Xiaoyi Liu,
Cheng Zhang,
Shaolong Wu,
Xiaoming Yuan,
Linglong Zhang,
Xiaofeng Li,
Jiong Yang
Published: Mon, 19 May 2025 00:41:53 -0700
Small, EarlyView.
Feed: Wiley: Advanced Materials: Table of Contents
Authors: Xinxin Zhang,
Hailong Yu,
Liubin Ben,
Guanjun Cen,
Yang Sun,
Liping Wang,
Junfeng Hao,
Jing Zhu,
Qiangfu Sun,
Ronghan Qiao,
Xiayin Yao,
Heng Zhang,
Xuejie Huang
Published: Mon, 19 May 2025 00:37:45 -0700
Advanced Materials, EarlyView.
Authors: Victor O. Kompanets,
Suge Feng,
Yiqi Zhang,
Yaroslav V. Kartashov,
Yongdong Li,
Sergei A. Zhuravitskii,
Nikolay N. Skryabin,
Alexander V. Kireev,
Ivan V. Dyakonov,
Alexander A. Kalinkin,
Ce Shang,
Sergei P. Kulik,
Sergey V. Chekalin,
Victor N. Zadkov
Published: Mon, 19 May 2025 00:31:13 -0700
Advanced Materials, EarlyView.
Feed: Wiley: Advanced Functional Materials: Table of Contents
Authors: Manoj Kumar,
Kritika Bhattacharya,
Samaresh Das
Published: Mon, 19 May 2025 00:46:52 -0700
Advanced Functional Materials, EarlyView.