Materials Science
Stacking-Engineered Switchable Altermagnetism in Topological FeSe bilayer systems
Jie Li, Shifang Li, Mengyang Zhang et al. (+3 more)
Altermagnetism and topological
insulators represent two of the most transformative frontiers in modern condensed matter physics, spintronics, and
quantum information science. Bringing these two paradigms together opens a largely unexplored route toward fundamentally new
quantum phenomena. Here, we predict a topological altermagnetic phase in
bilayer tetragonal Fe-based
superconductors and reveal it as a highly tunable platform for valley-polarized anomalous
Hall physics. Based on first-principles calculations, we show that the characteristic
spin-splitting and valley polarization can be effectively tuned via applied strain. Moreover, the resulting valley-polarized anomalous
Hall conductivity can be manipulated by shifting the
Fermi level. These findings reveal a powerful route for controlling altermagnetism in topological materials and identify a realistic material platform for its experimental realization and technological exploitation.
Read the full abstract ▾
All authors Jie Li, Shifang Li, Mengyang Zhang, Pan Zhou, Jianxin Zhong, Ruqian Wu
Other Condensed Matter
Phase-dependent parametric amplification of propagating spin waves in YIG nanostructures enabled by local inhomogeneities
Akira Lentfert, Ephraim Spindler, Björn Heinz et al. (+2 more)
As magnonics evolves towards non-conventional computing, the development of phase-conserving and phase-sensitive amplification mechanisms becomes increasingly important. A particularly promising approach is non-adiabatic parametric amplification. In this work, the influence of local inhomogeneities on the parallel parametric amplification of
spin waves in nano-scale Yttrium Iron Garnet waveguides is investigated. Micromagnetic simulations reveal that in larger pump regions, where only adiabatic amplification is expected, scattering centers provide additional linear momentum that enables non-adiabatic amplification of propagating
spin waves. Importantly, the coherence of the process remains unaffected by the scattering and the generation of co-propagating
spin waves enhance the effective amplification. Our simulations are confirmed by micro-focused Brillouin light scattering spectroscopy experiments, reproducing both the phase-dependent behavior and the characteristic features of the time-resolved dynamics. These findings demonstrate the flexibility of the parametric amplification process and provide a key mechanism for the development of large-scale
spin-wave computing
circuits.
Read the full abstract ▾
All authors Akira Lentfert, Ephraim Spindler, Björn Heinz, Mathias Weiler, Philipp Pirro
Mesoscale and Nanoscale Physics
Moire-Engineered Excitonic Landscape and Phonon-Mediated Recombination in Twisted WSe2 Bilayers
Memansa Thapa, Aksa Thomas, Jayalekshmi U. J. et al. (+7 more)
We report light emission from the moire superlattice of a twisted
bilayer of tungsten diselenide (WSe2/WSe2) encapsulated in insulating hexagonal boron nitride (hBN). The low-temperature photoluminescence (PL) spectroscopy reveals signatures of moire-potential induced strong interlayer excitonic emission and
phonon-assisted recombination, while the twisting significantly suppresses the emission from localized defect-bound
excitons. The moire potential redistributes carriers into indirect valleys, thereby enhancing recombination efficiency and stabilizing the interlayer
excitons. Our findings establish that precise control of twist angle and dielectric environment provides a new route for engineering excitonic systems for exploring
exciton-
phonon interactions and associated
quantum phenomena in transition metal dichalcogenides.
Read the full abstract ▾
All authors Memansa Thapa, Aksa Thomas, Jayalekshmi U. J., Krishna Prasad Bera, Darshit Solanki, Kenji Watanabe, Takashi Taniguchi, Ajay Kumar Shukla, Anindya Das, Ajay Soni
Soft Condensed Matter
Roughness-controlled Tribocharging Governs Friction in Dry Glass Contacts
Liang Peng, Begum Demirkurt, Thibault Roch et al. (+3 more)
Friction is commonly reduced by polishing surfaces, based on the idea that roughness enhances mechanical interlocking and thus friction. Here we show that, for dry glass-glass contacts, increasing nanoscale roughness can instead reduce friction because it suppresses triboelectric adhesion. Using rheometer-based friction measurements in dry nitrogen, super-resolution imaging of the real contact area, soft x-ray discharge, and Faraday-cup electrometry, we demonstrate that sliding generates substantial tribocharges whose electrostatic attraction contributes significantly to friction. As the root-mean-square surface slope h'_rms of the glass ball is increased from 0.01 to 0.09, the real contact area and retained tribocharge both decrease strongly, while the average contact pressure increases by a factor of three; nevertheless, the friction coefficient drops by about 30%. Discharging the interface with soft x-rays largely removes the roughness dependence of friction. Our results show that nanoscale roughness controls tribocharging and electroadhesion in dielectric contacts, inverting the classical relation between roughness and friction and identifying triboelectric effects as a key design parameter for friction control.
Read the full abstract ▾
All authors Liang Peng, Begum Demirkurt, Thibault Roch, Albert M. Brouwer, Bart Weber, Daniel Bonn
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Attention-Like Hebbian Learning from Quantum Probability Flow and Quantum-Annealer Tests
Masayuki Ohzeki
We propose a
quantum probability-flow principle for deriving local learning rules in associative
memory. A transverse field defines leakage channels from data states, and minimizing the measured survival loss gives stability-driven updates. For imaginary-time, dephased dynamics, the local leakage free energy is the log-sum-exp of energy gaps; its gradient is a softmax-weighted Hebbian rule. Real-time stability instead yields a power-law weighting. D-Wave standard- and fast-anneal tests of a one-hot
attention forward map are better fitted by an effective softmax than by a Lorentzian power law.
Read the full abstract ▾
Strongly Correlated Electrons
Anisotropic Moiré Fractional Chern Insulators and Their Phase Transitions
Bo Peng and Jin-Xin Hu
Recently, moiré
heterostructures have been observed to host fractional Chern
insulator (FCI) phases at zero
magnetic field. In this work, we show that the FCI phases are robust against moderate
lattice anisotropy, while sufficiently strong anisotropy drives
quantum phase transitions from incompressible topological phases to competing charge-density-wave (CDW) and
Fermi-
liquid (FL) phases. Specifically, in the case of twisted transition metal dichalcogenides (such as MoTe$_2$), the anisotropy arises from an interlayer momentum shift induced by heterostrain. We find that increasing anisotropy suppresses the many-body topological gap, eventually destabilizing the fractional topological phase. Beyond a critical anisotropy value, the system gradually transitions to a
symmetry-broken state characterized by stripe-like CDW order. It has a Landau Level counterpart, where effective mass anisotropy provides an additional tuning knob for the fractional
quantum Hall state; sufficiently strong anisotropy drives a transition to a charge-ordered phase. Moreover, in the anisotropic ideal Chern band model with
lattice stretching, a
Fermi liquid phase emerges as anisotropy increases. Our results establish that anisotropy provides a direct route for engineering and exploring competing correlated phases in FCI states based on moiré materials.
Read the full abstract ▾
Materials Science
Charge dynamics in the Weyl semimetals NbIrTe$_4$ and TaIrTe$_4$ under pressure: Signatures of an electronic phase transition
M. Lamp, J. Ebad-Allah, A. Chmeruk et al. (+7 more)
A high-pressure investigation of the Weyl semimetals NbIrTe$_4$ and TaIrTe$_4$ is presented, using infrared spectroscopy supplemented by density functional theory calculations. The experimental optical conductivity spectra as a function of pressure suggest the occurrence of a pressure-induced phase transition at a critical pressure $P_\text{c}=7\text{--}8$ GPa. This transition is most likely electronic in nature, as Raman scattering measurements provide no evidence of a significant structural phase transition. Above $P_\text{c}$ a significant redistribution of spectral weight occurs in the optical conductivity spectrum for both materials. A Drude-Lorentz analysis of the optical data indicates a sharp reduction in the free carrier concentration at $P_\text{c}$, concomitant with the appearance of a low-energy
phonon, which was initially screened by free charge carriers. A predominantly electronic origin of the phase transition is supported by the calculated electronic band structure,
Fermi surface, and interband optical conductivity as a function of pressure. Our findings provide collective evidence for a pressure-induced, most likely electronic phase transition in both van der Waals materials at $P_\text{c}=7\text{--}8$ GPa, highlighting the tunability of their electronic band structure by hydrostatic pressure.
Read the full abstract ▾
All authors M. Lamp, J. Ebad-Allah, A. Chmeruk, N. Bura, R. Schönemann, L. Balicas, S. H. Lee, Z. Q. Mao, L. Chioncel, C. A. Kuntscher
Materials Science
Deep Learning-Accelerated Dynamic Kinetic Monte Carlo Simulation for Hydrogen Transport in Tungsten
Seiki Saito, Keisuke Takeuchi, Hiroaki Nakamura et al. (+5 more)
In
magnetic confinement fusion reactors, hydrogen
plasma irradiation causes material saturation and recycling, where hydrogen released from the tungsten wall significantly impacts the peripheral
plasma. Kinetic Monte Carlo (kMC) simulations are essential for investigating the dynamic balance between incident and emitted fluxes at the atomic scale. However, standard kMC frameworks are inadequate for handling realistic material complexities, such as polycrystalline structures and dynamic
evolution under irradiation, being computationally bottlenecked by continuous transition parameter updates. Conventionally, evaluating migration barriers in disordered systems (e.g., grain boundaries) relies on computationally prohibitive on-the-fly atomistic calculations like the Nudged Elastic Band (NEB) method. Here, we present a deep learning-accelerated Dynamic kMC framework that eliminates this reliance. Our approach integrates a three-stage deep learning pipeline: a pix2pix model for predicting local 3D potential energy distributions, a U-Net for extracting hydrogen trapping sites, and a 3D-CNN for directly evaluating migration barriers. To achieve macroscopic timescales, we implemented a hierarchical spatial index combined with a differential local-update
algorithm operating in O(1) complexity. This architecture restricts recalculations to the immediate vicinity of moving atoms, accelerating updates. Demonstrated on a large-scale realistic polycrystalline tungsten model, the framework successfully reproduces preferential hydrogen trapping along grain boundaries, bridging the gap between atomic-scale accuracy and macroscopic timescales for full-scale
plasma-wall interaction simulations.
Read the full abstract ▾
All authors Seiki Saito, Keisuke Takeuchi, Hiroaki Nakamura, Yasuhiro Oda, Kazuo Hoshino, Yuki Homma, Shohei Yamoto, Yuki Uchida
Materials Science
Giant dielectric permittivity in Nb-doped rutile crystals
D. Nuzhnyy, V. Bovtun, J. Petzelt et al. (+13 more)
Dielectric properties of Nb-doped (~1.5 at%) rutile single
crystals were studied in the 10-300 K temperature range (at frequencies below the MHz range down to 0.3 K) in a broad frequency range, up to terahertz and infrared range, to understand the origin of its
giant permittivity. The results were fitted, modelled and compared with those of the undoped rutile
crystal measured in the terahertz and infrared ranges. The primary effect originates from the near-electrode depletion layer of lower conductivity compared to the bulk (surface barrier-layer capacitor effect), which causes a strong thermally activated relaxation in the MHz dielectric spectra. In the higher frequency range, the main difference between doped and undoped
crystals is the presence of an overdamped microwave excitation (central mode) in the doped
crystal for both polarizations, persisting down to 10 K and not thermally activated. This accounts for the previously reported permittivity increase, even at 2 K - where all lower-frequency relaxations are frozen - compared to undoped
crystals. It also explains why our low-frequency permittivity at 0.3K exceeds the THz value. The origin of this excitation remains unclear and requires further investigations. Doping affects polar
phonons only by slightly increasing their damping.
Read the full abstract ▾
All authors D. Nuzhnyy, V. Bovtun, J. Petzelt, M. Savinov, M. Kempa, P. Levinský, P. Vaněk, T. Kmječ, T. Ostapchuk, P. Kužel, J. Hlinka, D. Crandles, M. Cosco, Y. Hashimoto, H. Taniguchi, S. Kamba
Soft Condensed Matter
SPOCK*: A simple program for simulating knotted and concatenated polymer rings off-lattice
Franco Ferrari and Marcin R. Piątek
The purpose of this work is to present SPOCK*, a Monte Carlo code specifically written to investigate the thermodynamic and mechanical properties of
polymers in the presence of topological constraints. The interactions between the monomers are described by a Lennard-Jones potential. Pulling forces can be applied to one or more monomers. Simple and fast
algorithms have been implemented to preserve the
topology and to compute the energy of the sampled conformations. After a new conformation is accepted, only the difference of energy between the new and the old conformations needs to be evaluated. In this way the simulation time grows linearly with the
polymer size. A strategy based on the fluctuations of the specific heat capacity has been developed in order to avoid bottlenecks like the trapping of the system in a deep local minima at low temperature. Currently, the averages of the following observables are computed: specific heat capacity, elongation and gyration radius.
Read the full abstract ▾
Disordered Systems and Neural Networks
A Minimal Duality Estimate for the Surface-Code Threshold under Nearest-Neighbor Correlated Errors
Masayuki Ohzeki
We apply the single-equation duality criterion to the square-octagonal random-bond Ising model recently obtained from an exact error-edge map for a surface code with nearest-neighbor correlated errors. The calculation is performed for the minimal
cell after the error-edge reduction. For the symmetric case \(p_1=p_2=p_3=p\), this gives \(p_c=0.0288427147\), in close agreement with the reported numerical threshold of about \(3\%\).
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from hep-th
Successes and challenges of using Semidefinite Programming for the study of Spin Chain Hamiltonians
David Berenstein and P. N. Thomas Lloyd
We study semidefinite programming (SDP) methods to analyze
spin chain
Hamiltonians. We examine the ground state energy, the first excited charged states and ground state correlators in two simple models: the Ising model in a transverse
magnetic field and the closely related 3-state Potts model. Our goal is to understand precisely what the SDP program is doing and when it works well, why it does so. We focus on the following novel ingredients: using charge constraints to obtain excited states and to see if additional constraints from integrable models are effective at improving the method. At criticality we also explore to what extent we can use approximate Virasoro correlators to extract conformal data: the central charge and some critical exponents of charged states. We also use these to identify the location of the phase transition. In the special case where the system is made of free
fermions we prove that the SDP finds the exact energy of the ground state and produces the correct two point functions of the
fermions. Away from free
fermion theories, the SDP gets progressively worse at estimating data beyond the value of the ground state energy (like correlation functions), although it qualitatively matches these. In order to be effective, the SDP seems to run into scaling issues where the amount of input needed scales poorly with the
lattice volume.
Read the full abstract ▾
Other Condensed Matter · Cross-listed from physics.optics
Bragg-enhanced time-domain Brillouin scattering from a propagating acoustic grating
O.S. Ken, D.O. Horiachyi, V. L. Korenev et al. (+4 more)
Generation and detection of coherent
phonons in
semiconductors by femtosecond optical pulses is a powerful tool for high-frequency acoustic control of their electronic properties. Here, we demonstrate a propagating one-dimensional acoustic grating in bulk
semiconductors using above-band-gap excitation by a train of
laser pulses with high repetition rate of 1 GHz. This approach enables shaping of the coherent acoustic
phonon spectrum and leads to a significant enhancement of Brillouin light scattering at selected probe wavelengths in pump-probe configuration. We demonstrate this effect at a cryogenic temperature of 5 K in prototypical
semiconductor systems, namely bulk crystalline GaAs and (Cd,Zn)Te, which serve as
benchmark materials for the proposed method. The spectral dependence of the time-domain Brillouin light scattering amplitude exhibits resonant peaks at discrete probe wavelengths arising from Bragg reflection of the probe light by the propagating acoustic grating. A 10-30-fold resonant enhancement of the signal amplitude is observed for GaAs and (Cd,Zn)Te, determined by the finite spectral width of the probe pulse. With further spectral narrowing, enhancements of the order ~ 100-150 are expected, set by the number N of strain pulses in the acoustic grating within the sample and ultimately limited by the material parameters and sample thickness.
Read the full abstract ▾
All authors O.S. Ken, D.O. Horiachyi, V. L. Korenev, A. V. Trifonov, I. A. Akimov, D. R. Yakovlev, M. Bayer
Statistical Mechanics
Linear optimal protocol for physical constraints in weakly driven processes
Pierre Nazé
The minimization of irreversible work in weakly driven systems within linear response under physical constraints on the protocol derivative is studied. The problem reduces to a shifted
eigenvalue equation involving the relaxation function. Owing to its dependence on time differences and its evenness, the relaxation kernel is naturally defined over a symmetric interval, where a periodic representation arises as a consistent closure that restores continuous translational invariance. Also, it shows how the irreversible work is defined in practice. Within this framework, the operator becomes diagonal in a
Fourier basis. The global optimal solution is the zero mode, yielding a constant driving speed and a linear protocol. The corresponding optimal work depends only on the integrated relaxation function. Numerical results obtained via genetic programming confirm the robustness of this solution across different kernels.
Read the full abstract ▾
Strongly Correlated Electrons
Spin Dynamics from Niu-Kleinman Adiabatic Approach and Slave Boson Mean Field Theory
Xuan Yang, Tianyang Xie, Shaohang Shi et al. (+2 more)
Spin-wave excitations provide a central probe of
magnetic order and electronic correlations in strongly correlated materials. In this work, we develop an adiabatic theory of
spin dynamics by combining the Niu-Kleinman formalism with Kotliar-Ruckenstein slave-
boson theory (NK+KRSB). For each frozen
spin configuration, the constrained slave-
boson saddle point is solved self-consistently, allowing the Berry-
curvature matrix and energy Hessian entering the linearized adiabatic equations of motion to be extracted directly. Applied to the half-filled single-orbital Hubbard model, the resulting
spin-wave dispersion shows substantially improved agreement with determinant
quantum Monte Carlo
benchmarks compared with the random phase approximation and closely approaches results from the time-dependent Gutzwiller approximation. We further extend the method to a two-orbital model of $\mathrm{La}_2\mathrm{NiO}_4$, demonstrating its applicability to realistic multi-orbital correlated systems. Because the approach only requires saddle-point solutions near the
magnetic ground state, it remains computationally efficient while incorporating strong-correlation effects beyond conventional weak-coupling descriptions, providing a practical framework for studying low-energy
spin excitations in correlated
quantum materials.
Read the full abstract ▾
All authors Xuan Yang, Tianyang Xie, Shaohang Shi, Kun Jiang, Jiangping Hu
Soft Condensed Matter
Molecular-to-polymeric crossover in ion diffusion in glyme-based electrolytes: from vehicular to hopping transport
Aicha Jani, Simon Gravelle, Pawel Wzietek et al. (+2 more)
Ion transport in glyme-based electrolytes arises from a complex interplay between solvation structure, ion correlations, and
polymer chain length. Here, combining pulsed-field gradient
nuclear magnetic resonance (PFG-NMR), ionic conductivity measurements, and molecular dynamics (MD) simulations, we investigate the
diffusion of monovalent cations (Li$^+$, Na$^+$, Cs$^+$) and TFSI$^-$ anions across a wide molecular-weight range, from monoglyme to long poly(ethylene
oxide) (PEO) chains up to 4000~g/mol, corresponding to $n$ up to 88, where $n$ is the number of ethylene
oxide repeat units. We identify a crossover region at $n \approx 8$ separating two transport regimes. For short chains, ion motion is consistent with a vehicular mechanism, accompanied by pronounced ion correlations. For longer chains, ion transport decouples from
polymer motion and proceeds via rapid coordination exchanges within a slowly relaxing
matrix. This transition is accompanied by reduced ion clustering and enhanced anion mobility, leading to increasingly anion-dominated charge transport. Overall, our results provide a molecular picture of ion transport across the molecular-to-polymeric transition and highlight the central role of solvation shell dynamics and
polymer relaxation in governing ion dynamics in glyme-based electrolytes.
Read the full abstract ▾
All authors Aicha Jani, Simon Gravelle, Pawel Wzietek, Mehdi Zeghal, Patrick Judeinstein
Mesoscale and Nanoscale Physics
Magnetic control of electron scattering in silicene quantum dots
Mohamed El Azar, Elmustapha Feddi, Pablo Díaz et al. (+2 more)
The Klein tunnel effect phenomenon makes it impossible to permanently confine charge carriers in massless nanostructures. However, applying a constant
magnetic field allows these electrons to be temporarily localized, thus forming quasi-bound states. In this study, we analyze the mechanism of electron
diffusion through a silicene
quantum dot (SQD) subjected to a perpendicular
magnetic field. To enhance spatial localization, we exploit the
spin-orbit coupling (SOC) specific to silicene, which generates a natural energy gap by acting as an effective mass. We first derive the solutions to the Dirac equation at low energy. Subsequently, by imposing the continuity conditions at the SQD interfaces, we obtain exact expressions for the
diffusion coefficients. These results are then used to map the scattering efficiency together with the spatial distributions of probability and current densities. Our simulations demonstrate that the presence of this intrinsic gap significantly enhances electron trapping at the center of the SQD. Finally, we prove that the interplay between the external field and SOC breaks
spin symmetry, thereby enabling robust and
spin-selective confinement.
Read the full abstract ▾
All authors Mohamed El Azar, Elmustapha Feddi, Pablo Díaz, David Laroze, Ahmed Jellal
Soft Condensed Matter
Stretching and bending of (really) thick elastic plates
Shiheng Zhao and Pierre A. Haas
The mechanical energy of an elastic plate separates into stretching and bending energies. This is a result for asymptotically thin plates, but it is often a surprisingly accurate approximation for thick plates, too. Here, we address this conundrum: We compute the deformations of a thick elastic plate resulting from imposed, asymptotically small deformations of its midline to discover effective stretching and bending
moduli. They soften with increasing plate thickness, but, strikingly, their ratio remains approximately constant. In this way, our calculations provide a justification for applying the thin-plate picture of stretching and bending to thick plates such as biological
cell sheets.
Read the full abstract ▾
Statistical Mechanics
Can the Brownian diffusion coefficient be reconstructed from Lyapunov exponents?
I. G. Marchenko, I. I. Marchenko, D. Ivashchenko et al. (+2 more)
We consider an ac-driven particle moving in a spatially periodic and symmetric potential. In the zero- temperature limit, for the analyzed parameter set, its dynamics is non-chaotic and the particle does not manifest diffusive properties. At non-zero temperatures, the asymptotic long-time motion follows normal (Brownian)
diffusion. Recent studies have shown that within tailored parameter regimes, the
diffusion coef- ficient is a quasiperiodic function of the external driving amplitude [1]. Although no general relation between Lyapunov exponents and Brownian
diffusion exists, we demonstrate that the quasiperiodic
diffusion coefficient at non-zero temperature can be accurately reconstructed from the maximal Lyapunov exponent of the corresponding deterministic system (at vanishing temperature). We propose an approximate formula for this purpose, which shows good agreement with numerical simulations, although some discrepancies are detected in the vicinity of the local maxima of the
diffusion coefficient. Finally, we examine the robustness of the correlation between
diffusion and the Lyapunov exponent under variations of the system parameters.
Read the full abstract ▾
All authors I. G. Marchenko, I. I. Marchenko, D. Ivashchenko, J. Łuczka, J. Spiechowicz
Materials Science
Interface Symmetry and Electrostatic Stabilization of Strain-Resilient Janus Heterobilayers for Flexible Piezotronics
Surender Kumar, Mostafa Torkashvand, Stefan Velja et al. (+1 more)
The electronic structure of conventional two-dimensional transition metal dichalcogenides (TMDs) is highly sensitive to
lattice deformation, often leading to indirect-to-direct band-gap transitions that compromise performance in flexible nanoelectronic applications. Janus TMDs, with their broken mirror
symmetry and intrinsic out-of-plane dipoles, offer a promising alternative platform for electrostatic tuning. However, their electronic stability under strain and the role of the chalcogen stacking sequence in their
heterostructures remains poorly understood. Here, we study from first principles the strain tolerance and piezoelectric properties of MoSSe/WSSe heterobilayers. By examining different configurations, we demonstrate that the interface chemistry strongly modulates interlayer coupling, dynamic charge redistribution, and dipole interactions. Importantly, the combined effects of intrinsic electric fields and interface electrostatics effectively suppress the strain-induced band-gap transitions typical of conventional TMDs. Moreover, while the in-plane piezoelectric response remains nearly insensitive to the stacking order, the shear piezoelectric coefficient depends heavily on the interfacial
symmetry and can be effectively tuned by strain modulation. Our results highlight interfacial engineering as a powerful route to design strain-resilient Janus
heterostructures for next-generation flexible optoelectronic, valleytronic, and piezotronic devices.
Read the full abstract ▾
All authors Surender Kumar, Mostafa Torkashvand, Stefan Velja, Caterina Cocchi
Strongly Correlated Electrons
Junha Kang and Taekoo Oh
The thermal
Hall effect (THE) probes charge-neutral excitations in
insulators, where the charge gap blocks electronic transport. Recently,
phonons have been shown to induce a THE comparable in magnitude to the
spin contribution, underscoring their critical role in thermal transport. Here, we develop a microscopic theory of the
phonon thermal
Hall effect (PTHE) in
chiral Mott
insulators. First, we derive the exact analytic form of the effective Raman interaction in half-filled Mott
insulators, showing that its strength is directly proportional to the scalar
spin chirality. Next, we demonstrate the intrinsic PTHE explicitly on the kagome
lattice. Crucially, our formulation reveals a temperature-dependent crossover in the transport behavior under isotopic substitution. Using this result, we establish a scaling law that quantitatively separates the
phonon contribution to the THE from other background signals. Our results not only provide the first fully microscopic derivation of the PTHE, but also establish a definitive experimental standard for isolating microscopic heat carriers in
chiral Mott
insulators.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Voltage-driven transition from steady-state fluctuations to phase-transition noise in nanoscale VO$_2$ devices
Sebastian Werner Schmid, Zoltán Balogh, Botond Sánta et al. (+6 more)
We investigate the electrically driven metal-to-
insulator transition (MIT) in nanoscale vanadium dioxide (VO$_2$) Mott memristor through noise spectroscopy and two-dimensional resistor network simulations. Our experiments focus on both the insulating phase as the applied voltage approaches the threshold voltage (set transition) and the metallic phase as the voltage is reduced toward the reset voltage (reset transition). In both regimes, we observe an order of magnitude increase in relative current noise near the transition points. To analyze the origin of this noise enhancement, we use simulations that capture the
stochastic dynamics of the phase transition. The simulations indicate that the increased noise stems from amplified phase fluctuations near the percolation threshold, where competing metallic and insulating domains lead to dynamic reconfiguration of the conduction paths. In addition, we show that the precursor current fluctuations observed near the switching threshold are consistent with the threshold voltage variability measured in repeated switching cycles, indicating that the noise sets a lower bound on the achievable variance. These findings offer key insights into the non-
equilibrium processes governing phase transitions in nanoscale VO$_2$ devices under electrical stimuli.
Read the full abstract ▾
All authors Sebastian Werner Schmid, Zoltán Balogh, Botond Sánta, Tímea Nóra Török, Zsombor Sinóros-Szabó, György Molnár, János Volk, László Pósa, András Halbritter
Quantum Gases
Two-body loss dynamics as a probe of dynamical bulk viscosity in ultracold atomic gases
Tingyu Zhang, Hiroyuki Tajima and Takeo Kato
We show that the
equilibrium connected correlation of the two-body loss rate provides access to the dynamical bulk viscosity in weakly dissipative
quantum gases. Starting from the Lindblad equation for weak inelastic losses, we derive the loss-current operator and, using a counting-field formulation of the loss statistics, the relation between the statistics of detected losses and the
equilibrium loss-rate correlator. The connected correlation of the two-body loss rate is found to be proportional to the
equilibrium contact correlation and hence to the bulk-viscosity spectrum. We show that the measured loss-counting covariance contains, besides the Poissonian self-correlation, a
quantum-jump backaction term of the same order as the target correlator, which is fixed by the transient of the mean loss rate after the loss is switched on. The bulk-viscosity spectrum can therefore be reconstructed from the combination of the loss-counting covariance and the mean loss dynamics. Our result identifies weak two-body loss dynamics as a probe of dynamical bulk viscosity, whose measurement has remained elusive in experiments.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from quant-ph
Coherent Exchange and Decoherence in Dirac-Spin-Liquid Quantum Interconnects
Dibakar Yadav and Rana Pratap
We develop a susceptibility-based open-system theory for two localized
qubits coupled through a candidate two-dimensional $\mathrm{U}(1)$ Dirac-
spin-
liquid-like bath. The central input is the gauge-invariant retarded physical
spin susceptibility $\Chi^R(q,\omega)$ of the bath. We show that this single response kernel controls both coherent and dissipative
qubit dynamics: its real part generates the nonlocal mediated exchange, while its absorptive part determines relaxation and dephasing through the
equilibrium noise spectrum. This gives a unified reduced two-
qubit description in which the usefulness of the bath as an
entanglement bus is governed by the competition between susceptibility-mediated exchange and bath-induced decoherence. As an analytically transparent
benchmark, we evaluate the spinon mean-field Dirac susceptibility and recover the static algebraic exchange $J_{\mathrm{eff}}(R)\propto J_{\rm local}^2/(v_F R^3)$, together with pseudogap-suppressed relaxation $\Gamma_1\propto J_{\rm local}^2\omega_0^3/v_F^4$. We then formulate a beyond-mean-field extension in which gauge-field dressing and other interaction effects are absorbed into a dressed physical susceptibility, without changing the reduced
qubit-sector mapping. The resulting framework provides a direct route from the many-body
spin response of a correlated two-dimensional bath to reduced-dynamics simulations of
entanglement generation, coherence loss, and the operational phase space of a candidate Dirac
spin-
liquid quantum interconnect.
Read the full abstract ▾
Soft Condensed Matter
Dynamical frustration in spacetime metamaterials enables cascading logic and synchronization
Rupesh Mahore, Oleksandr Gamayun, Guillaume Noetinger et al. (+3 more)
Spacetime metamaterials are engineered media whose constitutive parameters such as permittivity, permeability, stiffness, or mass density are modulated simultaneously in both space and time. These additional degrees of freedom, absent in conventional static metamaterials, unlock a cabinet of wave phenomena that cannot be achieved in time-invariant structures, e.g. compact nonreciprocal devices, topological
insulators, and devices for efficient frequency conversion and mixing and pulse shaping. The vast majority of these studies, however, operate in the stable regime, where modulation parameters are chosen to yield linear wave propagation. Here, we push spacetime metamaterials into the regime of parametric instability, and discover a novel type of “dynamically frustrated” oscillating states, where nonlinear non-reciprocal, topologically protected phase dislocations emerge. We control these dislocations and make them stop, split, and recombine. We harness this control to create devices for cascading logic in branched networks, and synchronization in 2D metamaterials. Our findings are broadly applicable anywhere where spacetime modulation can be pushed beyond linear stability, from cold atoms and superconducting
circuits to acoustics and RF
circuits.
Read the full abstract ▾
All authors Rupesh Mahore, Oleksandr Gamayun, Guillaume Noetinger, Romain Fleury, Corentin Coulais, Benjamin Apffel
Materials Science
Iterative Thermodynamic Augmentation of Spatially Resolved Analytic Microscopy for Fast-Diffusing Solutes
Santiago Benito, Louis Becker, Niels Jöns et al. (+1 more)
The spatially resolved quantification of fast-diffusing solutes presents several challenges in analytic microscopy. Given the critical role of interstitially alloyed elements in physical metallurgy, we propose a computational framework that addresses this limitation by augmenting spatially resolved composition maps of substitutional elements with computationally derived interstitial distributions. The underlying methodology is an iterative thermodynamic model: exploiting the stark differences in solid-state
diffusion kinetics, the model assumes a state of partial chemical
equilibrium exclusively for the mobile interstitial species. An optimization scheme iteratively adjusts an uniform interstitial chemical potential across the mapped microstructure until the integrated local concentration converges with an independently measured bulk value. Ultimately, this approach extracts thermodynamically consistent interstitial concentration maps from robust, low-noise microscopy data, yielding quantitative spatial arrays that are otherwise time- and resource-intensive to obtain at best.
Read the full abstract ▾
All authors Santiago Benito, Louis Becker, Niels Jöns, Sebastian Weber
Superconductivity
Evolution of the intertwining correlated topological phases in iron-based superconductor Fe(Te,Se)
Yue Sun, Shiying He, Zhongyi Zhang et al. (+16 more)
Multiple topological electronic phases can coexist within a single
quantum material and induce different topological superconducting states, offering deeper insights into interplay of topological superconducting states and Majorana modes, which may also be influenced and modified by correlation effect. Iron-based
superconductors, with both topological states and correlation effect, is an ideal platform to study these phenomena. Here, with high resolution angle resolved photoelectron spectroscopy, we directly resolve two distinct intertwining topological states in iron-based
superconductor Co-doped Fe(Te,Se), and study their
evolution with electron doping. We identify a region where both topological
insulator surface states and topological Dirac semimetal states intersect the
Fermi level. The topological states are affected by the strong correlation effect and are isolated from trivial bulk states. The
evolution between distinct topological phases offers a good opportunity to study various Majorana modes from different superconducting phases according to theoretical analysis. Our findings establish an ideal platform for exploring the interaction between multiple topological superconducting states and the related Majorana modes.
Read the full abstract ▾
All authors Yue Sun, Shiying He, Zhongyi Zhang, Yong Huang, Jingheng Chen, Weixiang Yan, Chunbo Yu, Yuyang Dong, Kohei Aido, Xin Zhou, Zhengtai Liu, Mao Ye, Jishan Liu, Haruhisa Kitano, Zhixiang Shi, Hong Ding, Takeshi Kondo, Xianxin Wu, Peng Zhang
Superconductivity
Excitonic-Superconducting Coexistence and Emergent Nematic Superconductivity Driven by Spontaneous Symmetry Breaking
Fei Yang, Ruigang Li, Junwei Liu et al. (+1 more)
Excitonic insulating (EI) and superconducting (SC) orders are generally regarded as mutually exclusive electronic instabilities. Within a self-consistent microscopic theory, we study electronic systems hosting an EI phase in the presence of SC pairing and show that an intrinsic mismatch between electron and hole
Fermi surfaces fundamentally reshapes this competition. This mismatch stabilizes FFLO-like electron-hole pairing and drives spontaneous
symmetry breaking of the EI state. The resulting
symmetry breaking reconstructs the pairing phase space for SC and EI state, such that different regions of the
Fermi surface complementarily support either EI or SC correlations, leading to a natural coexistence of the two orders. Notably, the emergent SC state consequently breaks rotational
symmetry and develops intrinsic nematic superconductivity, even in the absence of explicit
symmetry-breaking fields (such as
magnetic fields,
spin-orbit coupling, or bare band-structure anisotropy). Our results suggest that candidate materials such as monolayer 1T$'$-MoTe$_2$ and the square-net semimetal NaAlSi may provide promising platforms for observing this phenomenon. More broadly, these findings reveal a unique mechanism by which competing many-body orders generate electronic nematicity, suggesting a broader route toward spontaneous anisotropic electronic states in correlated
quantum materials.
Read the full abstract ▾
All authors Fei Yang, Ruigang Li, Junwei Liu, Binghai Yan
Materials Science
Polaron Transport in TiO$_{2}$ from Machine Learning Molecular Dynamics
Christian S. Ahart, Denan Li, Jochen Blumberger et al. (+1 more)
Transition metal
oxides have attracted much
attention as photo(electrochemical)-catalysts but practical applications are typically hampered by their low and anisotropic charge mobility. A deep understanding of excess charge carrier transport in these materials requires a dynamical treatment of
nuclear motion that goes well beyond standard approaches. Here we introduce DeepPolaron, a machine learning framework boosting the accessible time scale of first principles molecular dynamics of adiabatic polaron transport by three orders of magnitude at a virtually negligible loss in accuracy. We apply our method to excess electron and hole transport in titanium dioxide rutile and anatase. We find that the excess electron in rutile relaxes to a polaron predominantly localized on a single Ti atom with hopping occurring only along the [001] direction, associated with an activation energy of 39 meV and a room temperature mobility of $4.4 \times 10^{-2}$ cm$^2$/Vs in good agreement with experiment. In contrast the hole polaron in anatase is localized on a single O atom, and due to poor O 2p orbital overlap with first nearest neighbors charge transport occurs primarily to second nearest neighbors, with a large activation energy of 139 meV resulting in a small room temperature mobility of $1.4 \times 10^{-3}$ cm$^2$/Vs. This work provides a finite temperature first-principles characterization of small polaron transport in rutile and anatase, with a methodology that is directly transferable to other small polaron forming materials and interfacial charge-transfer processes.
Read the full abstract ▾
All authors Christian S. Ahart, Denan Li, Jochen Blumberger, Shi Liu
Soft Condensed Matter
Stress relaxation in fiber networks via force-dependent stochastic severing
Prathamesh Kulkarni, Anatoly B. Kolomeisky and Fred C. MacKintosh
Fiber networks contribute to the mechanical stability of various biological systems, from
cells to tissues. Such systems have been modeled by networks of springs or fibers that exhibit
rigidity transitions as a function of either connectivity or applied strain. For a fiber network under constant applied strain, severing can reduce the connectivity and destabilize an initially rigid structure. Here, we investigate stress relaxation in spring and fiber networks in the presence of
stochastic, force-dependent severing. A computational model to predict stress relaxation with mechanochemical feedback of stress on severing is developed. We also examine the effects of severing on the network
topology and onset of
rigidity transition. Using 2D triangular
lattice-based computer simulations, we explore different limits of the feedback and demonstrate the shift in the onset of
rigidity depending on the limit. The limit of tension-suppressed severing delays stress relaxation and shifts the transition into the bending-dominated regime to lower-than-expected connectivity. In contrast, tension-enhanced severing accelerates relaxation and shifts the transition to higher-than-expected connectivity. It is also found that the magnitude of this shift depends on the applied shear strain and the strength of the feedback. Our theoretical approach clarifies some microscopic aspects of these phenomena. Understanding the impact of such feedback mechanisms can provide valuable insights into designing systems by tuning the feedback to the desired response.
Read the full abstract ▾