Superconductivity
Interference-Enhanced Large Electron-Phonon Coupling from Raman-active Breathing Modes in Moiré Semiconductors
Ning Mao, Shaozheng Wang, Cheng Xu et al. (+6 more)
Superconductivity was recently observed in twisted WSe2 and MoTe2, raising a central question: is the pairing driven by electronic correlations, by
phonons, or by both? Answering it requires determining the electron-
phonon coupling (EPC) in these moiré
semiconductors, whose calculation in realistic supercells of thousands of atoms lies beyond the reach of direct first-principles methods. Here we combine filling-dependent Raman spectroscopy with machine-learning first-principles calculations to obtain the EPC mode by mode in supercells of up to tens of thousands of atoms. Raman reveals only a few moiré
phonons whose frequencies shift strongly with filling; we trace this to an interference selection rule: a
phonon couples strongly only when its displacement texture matches the static
lattice-reconstruction pattern, and is otherwise suppressed by destructive interference. The rule selects the low- and high-frequency breathing modes seen in Raman and makes the coupling peak at large twist angles, near those at which superconductivity appears.
Lattice-reconstruction interference thus emerges as an organizing principle for moiré EPC, pointing to a substantial, potentially dominant,
phonon contribution to large-angle pairing.
Read the full abstract ▾
All authors Ning Mao, Shaozheng Wang, Cheng Xu, Xumin Chang, Kenji Watanabe, Takashi Taniguchi, Claudia Felser, Shengwei Jiang, Yang Zhang
Mesoscale and Nanoscale Physics
Extended Landau–Lifshitz equation for nanomagnets: a path-integral derivation of surface-induced magnetization nutation
H. Kachkachi and P. Thibaudeau
An effective dynamical equation for the magnetization of a nanomagnet with surface anisotropy is derived from an atomistic
spin Hamiltonian using the
spin coherent-state path integral formalism. The derivation proceeds in two steps. First, the continuum Euclidean action for the many-
spin nanomagnet is obtained, including the Wess–Zumino–Witten (Berry phase) term, as well as exchange, Zeeman, and core/surface anisotropy contributions. Second, the local magnetization density is decomposed into a slowly varying macrospin component and transverse
spin-misalignment fluctuations driven by surface effects. A systematic expansion of the action is then performed up to quadratic order in the transverse-fluctuation variables. Under the adiabatic approximation, in which transverse modes relax much faster than the macrospin, these modes are eliminated by using their static Green's function solution. This results in a closed, extended Landau–Lifshitz equation for the macrospin, featuring an effective field with nontrivial corrections from
spin misalignment. These corrections renormalize both the Zeeman and anisotropy fields and introduce additional terms that act as nutation- and damping-like contributions. ... Together, these results establish a microscopic foundation for surface-induced magnetization nutation in nanomagnets and provide a framework to estimate corrections to the precession frequency and effective damping. The corresponding shift in the
ferromagnetic-resonance frequency and linewidth is measurable with standard GHz spectrometers, and the underlying adiabatic-elimination mechanism is expected to generalize to any slow
magnetic variable coupled to a bath of fast-fluctuating modes.
Read the full abstract ▾
Quantum Gases
Ab initio path integral Monte Carlo study of the 2D uniform electron liquid at finite temperatures
Tobias Dornheim, Fotios Kalkavouras, Paul Hamann et al. (+3 more)
We present extensive ab initio path integral Monte Carlo (PIMC) simulations of the two-dimensional uniform electron gas (2DEG), covering a broad range of density parameters $r_s=0.1,\dots,50$ and temperatures $\Theta=k_\textnormal{B}T/E_\textnormal{Fermi}=0.5,\dots,16$. This allows us to analyze various structural, linear density response and spectral properties. We find clear evidence of a roton-type feature in the dynamic structure factor at strong coupling and intermediate wavenumbers. We also
benchmark novel dielectric theory implementations for the 2DEG~[Kalkavouras et al.~arXiv:2601.14989] for structural and spectral properties across the
liquid phase diagram. The PIMC results can be used to
benchmark existing theories and approximations, and guide the development of new methodologies.
Read the full abstract ▾
All authors Tobias Dornheim, Fotios Kalkavouras, Paul Hamann, Zhandos A. Moldabekov, Jan Vorberger, Panagiotis Tolias
Quantum Gases · Cross-listed from gr-qc
Sonic black holes with thick horizons in BECs
Daniel Peñalver, Marco De Vito, Roberto Balbinot et al. (+1 more)
We consider simple one dimensional models of acoustic black holes formed by Bose-Einstein condensates where the flow is stepwise homogeneous. We shall concentrate on the case in which an extended sonic region is present, i.e. a region where the flow velocity equals exactly the speed of sound. These models can be thought of as acoustic black holes with a thick horizon. Particular
attention will be devoted to the number of created particles and to the density-density correlation functions, these latter being at present time the experimental tool to identify Hawking like radiation in acoustic black holes.
Read the full abstract ▾
All authors Daniel Peñalver, Marco De Vito, Roberto Balbinot, Alessandro Fabbri
Soft Condensed Matter
A method for measuring the dispersion of elastic waves in disordered computer-solids
Edan Lerner
The dispersion of elastic waves in disordered solids plays a key role in determining the vibrational density of states and harmonic wave attenuation rates. As such, the availability of robust computational approaches to the precise extraction of the dispersion is of key importance. Here we present a simple method – the imposed wave method (IWM) – , which provides direct access to the dispersion of elastic waves in computer models of solids, without any fitting involved. We directly
benchmark the method against the `ground-truth' obtained from direct diagonalization of solids' hessian
matrices, to find good agreement. We discuss limitations of and finite-size effects in the method, and show that exploiting the method's finite-size scaling provides access to a fundamental quantifier of mechanical disorder that determines wave attenuation rates and spectral widths.
Read the full abstract ▾
Materials Science
Amorphous materials as a frontier challenge for universal interatomic potentials
Natascia L. Fragapane and Volker L. Deringer
Pre-trained or 'foundational' machine-learned interatomic potentials (MLIPs) are now widely used in materials modelling. However, early pre-trained models and
benchmarks have largely focused on ordered, crystalline structures, and their transferability to non-crystalline solids remains unclear. Here, we show that the amorphous state is indeed a central challenge for future universal MLIPs, based on a systematic evaluation of current mainstream models in this domain. We introduce a benchmarking framework built on a curated reference
dataset of canonical amorphous systems, as well as validation for structures and properties. Our study identifies limitations in the transferability of many current pre-trained models and investigates fine-tuning strategies tailored to disordered phases. Together, our results can facilitate future applications of MLIPs in the fast-growing field of amorphous functional materials, and they provide guidance for designing next-generation training
datasets and transferable atomistic models.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from quant-ph
Toward Quantum Utility in Correlated Topological Matter: Variational Preparation of Fractional Quantum Hall Manifolds
Sergio F. Expósito, Unai Aseginolaza, Raúl Guerrero-Avilés et al. (+3 more)
We investigate the use of variational
quantum algorithms to prepare and characterize fractional
quantum Hall states on near-term
quantum processors. Focusing on the $\nu=1/3$ Laughlin phase described by the $V_1$ Haldane pseudopotential, we formulate the lowest-Landau-level problem in second quantization, and implement particle-number-preserving variational
circuits combined with the variational
quantum eigensolver (VQE) and variational
quantum deflation (VQD). We
benchmark the approach in two complementary geometries: Haldane sphere and
torus shape. On the Haldane sphere, the target state is a unique zero-energy Laughlin ground state, providing a controlled test of the variational workflow and of excited-state reconstruction. On the
torus, the problem retains the genuinely two-dimensional periodic character of the
quantum Hall liquid and exhibits the threefold topological ground-state degeneracy expected for the $\nu=1/3$ fractional filling factor. This feature makes the
torus a more demanding
benchmark than the quasi-one-dimensional cylinder or thin-
torus limits commonly exploited in state-preparation
quantum protocols. We
benchmark the hardware-optimized variational states against exact diagonalization using energy estimates, error-mitigated observables, and subspace-containment diagnostics. Our results show that hybrid
quantum algorithms can approximately reconstruct the low-energy structure of small fractional
quantum Hall systems, including the topological ground-state
manifold on the
torus. Beyond serving as a
benchmark for
quantum hardware, this geometry-resolved approach provides a route toward
quantum simulations of fractional Chern
insulators and strongly correlated topological phases in realistic two-dimensional materials.
Read the full abstract ▾
All authors Sergio F. Expósito, Unai Aseginolaza, Raúl Guerrero-Avilés, Joaquim Jornet-Somoza, Francisco Guinea, Juan Borge
Strongly Correlated Electrons
Conformal Nature of Quantum Phase Transitions via Fuzzy Three-Sphere Regularization
Xue Meng, Liangdong Hu and Wei Zhu
Conformal field theory (CFT) offers a modern viewpoint for understanding phase transitions. However, directly accessing the conformal
algebra and microscopically uncovering the emergent conformal
symmetry, especially in higher dimensions, remains a significant challenge. Motivated by recent advances in revealing CFT features via the fuzzy two-sphere, here we generalize this approach to higher dimensions and aim to expose the conformality at the (3+1)-D
quantum critical point. We demonstrate this framework by investigating
quantum phase transitions belonging to the Ising and Yang-Lee universality classes in a (3+1)-D
quantum model (equivalent to a classical four-dimensional system), realized via Landau level projection on the fuzzy three-sphere. By computing the energy spectra at criticality, we explicitly verify the state-operator correspondence, a hallmark of conformal invariance. Together with prior advances, this work establishes a new pathway for the microscopic study of emergent conformality in higher-dimensional phase transitions.
Read the full abstract ▾
Superconductivity
Iron-Based Superconductors: A Decade of Materials, Magnetism, and Mechanisms
Xingye Lu, Hechang Lei, Jun Zhao et al. (+2 more)
Since its discovery in 2008, iron-based
superconductors (FeSCs) have become a central platform for exploring high-temperature superconductivity in multiband, electron-correlated materials. This review focuses on major developments over the past decade or so, emphasizing experimental advances, pairing mechanisms, and emerging applications. Structural tuning through chemical substitution, pressure, and epitaxial growth enables precise control of the electronic,
magnetic, and superconducting ground states, thereby revealing their interplay. In particular, the electronic nematic phase and stripe-type
antiferromagnetic order-often coexisting or competing-are central to understanding the phase diagrams.
Spin waves in magnetically ordered parent compounds and
spin excitations (fluctuations) in doped
superconductors are extensively characterized by inelastic
neutron scattering. While high-energy
spin excitations in doped
superconductors retain substantial spectral weight across a wide energy range reminiscent of
spin waves in their undoped parents, the low-energy response reveals a collective
spin excitation termed "resonance" coupled to superconductivity. The momentum structure of superconductivity-induced resonance provides strong evidence for sign-changing pairing in many FeSCs, while disorder effects, orbital-fluctuation scenarios, quasiparticle damping, and compound-dependent gap structures indicate that $s_{\pm}$, $s_{++}$, nodal $s$, $d$-wave, and multicomponent states must be discussed in a material-specific framework. Advances in thin-film growth, intercalation chemistry, and interface engineering-particularly in FeSe-based systems-have enabled enhanced $T_{c}$ and novel device geometries. With high upper critical fields, moderate anisotropy, and improving current densities, FeSCs continue to drive both fundamental insight and technological applications in superconductivity.
Read the full abstract ▾
All authors Xingye Lu, Hechang Lei, Jun Zhao, Hideo Hosono, Pengcheng Dai
Materials Science
PAC Studio Machine Learning: Human-in-the-Loop Analysis of TDPAC Spectra
Thien Thanh Dang, Juliana Heiniger-Schell and Doru Constantin Lupascu
Time-differential perturbed angular correlation (TDPAC or PAC) analysis is an ill-conditioned inverse problem in which site count, interaction type, correlated hyperfine parameters, damping, and initialization choices can produce competing numerical solutions. This software paper presents PAC Studio ML, a human-in-the-loop Python desktop environment for physics-informed inverse analysis of PAC spectra. The software integrates a
Hamiltonian-based forward PAC model, user-defined synthetic training libraries, feature extraction, one-, two-, and three-site machine-learning predictors, direct parameter prediction, Auto sites model-family screening, ML-seeded nonlinear least-squares refinement, visualization, benchmarking, diagnostics, model-card reporting, and export tools. The ML component is designed to support, not replace, conventional fitting and expert interpretation by accelerating parameter exploration, suggesting plausible initialization regions, comparing site-count hypotheses, and improving reproducibility. Held-out synthetic tests demonstrate proof of operation and illustrate the unequal recoverability of PAC parameters in difficult inverse problems. Selected BiFeO3 examples demonstrate conventional, direct-ML, ML-seeded, and Auto sites workflows as software case studies, not as a complete experimental validation corpus. PAC Studio ML is therefore positioned as a supporting tool for expert PAC analysis: it improves workflow speed and diagnostic transparency while final model choice, physical constraints, and materials interpretation remain the responsibility of the researcher.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Mode-locking instability and multiple soliton formation in GaN polariton waveguide cavities
O. Bahrova, V. Develay, H. Souissi et al. (+10 more)
We study the emergence of multi-
soliton regimes in 1D ridge polariton waveguides of two different lengths. We show that by varying the position of the gain, which in out-of-
equilibrium polariton systems is provided by the pumping
laser and its associated excitonic reservoir, it is possible to tune the regime of
soliton formation between single and multiple
solitons. This
soliton dynamics can be quantitatively reproduced by solving the Gross-Pitaevskii equations of the coupled
exciton-
photon system, which show that the
soliton splitting mechanism is governed by the
exciton reservoir dynamics.
Read the full abstract ▾
All authors O. Bahrova, V. Develay, H. Souissi, C. Brimont, L. Doyennette, B. Alloing, E. Cambril, S. Bouchoule, T. Ackemann, J. Zuniga-Perez, D. Solnyshkov, G. Malpuech, T. Guillet
Mesoscale and Nanoscale Physics
Tellurium Metasurface Beam Splitter with Pulse Laser-Controlled Anisotropy
Takuto Hiraoka, Mizuho Matoba, Yuta Kobayashi et al. (+5 more)
Laser-programmable optical anisotropy offers a new route to developing reconfigurable metasurfaces without conventional nanofabrication processes. Here, we demonstrate a lithography-free approach based on spatial control of the crystallographic $c$ axis orientation in tellurium (Te) using pulse
laser irradiation. As a proof of concept, we demonstrate a Te metasurface beam splitter by
laser-written optical-axis patterning and experimentally confirm that its optical response is in good agreement with theoretical predictions and numerical simulations. By directly programming the local optical anisotropy, this method enables a simple fabrication process while offering the possibility of rewriting and dynamically reconfiguring device functionality. These features make this approach a promising platform for non-resonant active metasurfaces and other reconfigurable flat-optics applications.
Read the full abstract ▾
All authors Takuto Hiraoka, Mizuho Matoba, Yuta Kobayashi, Arata Mitsuzuka, Masashi Kawaguchi, Haruyuki Sakurai, Kuniaki Konishi, Masamitsu Hayashi
Materials Science
Impact of Electronic Energy Dissipation on Primary Radiation Damage Formation in Silicon
Nadezda Korepanova, Rafael Nuñez-Palacio and Andrea E. Sand
In this work, we investigate the role of ion-electron coupling in simulations of radiation damage formation in silicon using molecular dynamics simulations within a two-temperature model. We explore predictions of a threshold-free approach to the coupling that accounts for both the electronic stopping and electron-
phonon coupling using a local electron density-based formalism. We compare two different coupling functions across a range of primary knock-on atom energies using two interatomic potentials. Our results demonstrate that the functional form of the ion-electron coupling plays a critical role in determining defect production efficiency, clustering, and recombination, and must therefore be carefully considered for accurate modeling of radiation damage formation. Furthermore, we find that the impact of the coupling in particular on the recombination of defects during the cooling phase of the cascade depends on the choice of interatomic potential, emphasizing the importance of physically grounded descriptions for both electronic effects and atom-atom interactions for reliable radiation damage predictions.
Read the full abstract ▾
Materials Science
Anisotropic hot carrier relaxation mediated by electron phonon scattering in TiN thin films
Hemant Verma, Tzu-Yu Peng, Shyr-Shyan Yeh et al. (+5 more)
Crystal orientations can shape the ultrafast energy relaxations of transition-metal nitride thin films. Here, we investigate the orientation-dependent electron-
phonon (e-ph) mediated relaxation in titanium nitride (TiN) thin films along the [100], [110], and [111] directions by combining first-principles calculations with ultrafast pump-probe transient absorption spectroscopy. Using maximally localized Wannier functions, we evaluate e-ph quasiparticle scattering lifetimes near the
Fermi level and identify a clear anisotropy: The TiN [111] orientation exhibits a longer e-ph scattering lifetime (15.96 fs) than [100] (13.69 fs) and [110] (11.12 fs), indicating reduced intrinsic e-ph scattering strength. Furthermore, we grew quasi-epitaxial, orientation-controlled TiN thin films on MgO substrates. Pump-probe measurements reveals that the population-level relaxation (hot-electron cooling) time also depends on orientations, with [111] films showing a significantly slower decay (110 fs) than [100] (90 fs) and [110] (80 fs). We emphasize that the calculated few-femtosecond scattering lifetimes and the measured few-hundred-femtosecond cooling time respectively represent single-event scattering and collective cooling, yet they exhibit consistent trends. These results demonstrate that crystallographic orientation provides a practical and powerful route to tune e-ph-governed relaxation in TiN thin films, offering essential design guidelines for refractory plasmonic and energy-conversion platforms.
Read the full abstract ▾
All authors Hemant Verma, Tzu-Yu Peng, Shyr-Shyan Yeh, Sheng-Chieh Huang, Pritam Sardar, Yang-Hao Chan, Yu-Jung Lu, Chao-Cheng Kaun
Materials Science
Anomalous Transverse Response and Multi-Field Ferrialtermagnetic-Ferroelectric Valve with CrSb Flakes
Long Zhang, Xinfeng Chen, Hongfei Liang et al. (+5 more)
Altermagnets combine the zero-stray-field of antiferromagnets with the
spin polarization of ferromagnets, showing great potential for spintronic applications. Here, we propose ferrialtermagnetism as a distinct subclass of altermagnetic family, where
symmetry-inequivalent altermagnetic sublattices possess nonidentical Neel vectors, preventing mutual cancellation of alternating
spin splitting and conferring intrinsic robustness against perturbations. This concept is realized in the three-atomic-layer CrSb (110) flakes, which exhibits
spin splitting of 344 meV, moderate uniaxial
magnetic anisotropy, and high Neel temperature of 657 K. The magneto-optical Kerr and the anomalous
Hall effects are observed. Integrating this ferrialtermagnetic CrSb with ferroelectric Sc2CO2 and Cu spacer, we design an ferrialtermagnetic-ferroelectric valve. This device displays
equilibrium tunneling magnetoresistance and electroresistance of ~10^3%, and non-
equilibrium magnitudes under bias, thermal, or light field reaches ~10^4% with high
spin filtering of 90%. The negative differential resistance and photogalvanic effects, and photocurrent extinction ratio of 283.8 are achieved. These findings establish ferrialtermagnetism as a fertile platform for multi-field-controlled, ultracompact, and self-powered spintronics and electronics.
Read the full abstract ▾
All authors Long Zhang, Xinfeng Chen, Hongfei Liang, Jianting Dong, Fei Zou, Yi Yan, Guangqian Ding, Guoying Gao
Materials Science · Cross-listed from physics.comp-ph
Uncertainty-Aware Structure-Property Mapping of Spinodoid Metamaterials via Heteroscedastic Gaussian Process Regression
Minwoo Park, Junseo Park, Mingyu Lee et al. (+4 more)
Spinodoid metamaterials offer a broad, tunable design space for anisotropic mechanical properties, yet their structure-property relationships are commonly treated as representative mappings from cone-angle descriptors to single effective stiffness values. This deterministic view overlooks the
stochastic nature of Gaussian random field (GRF)-based
topology generation, where identical cone-angle descriptors can produce different morphology realizations and property scatter. Here, we present an uncertainty-aware structure-property mapping framework that reinterprets cone-angle descriptors as
stochastic descriptors associated with input-dependent property distributions. Using heteroscedastic Gaussian process regression (GPR), the framework infers input-dependent predictive uncertainty from sparse one-realization-per-point data without requiring empirical variance labels at every design point. The results show that stiffness scatter differs across tensor components according to each component's mechanically active directions, and that parameter sets yielding identical mean stiffness can carry different aleatoric uncertainty. Applying this uncertainty to reliability-based design optimization (RBDO), we show that a deterministic optimum is highly susceptible to constraint violation once morphology-induced variability is considered, and that a homoscedastic RBDO formulation fails to meet the prescribed reliability target - only the heteroscedastic formulation satisfies the reliability target under the heteroscedastic uncertainty evaluation. This establishes uncertainty-aware surrogate modeling as essential for reliability-aware inverse design of spinodoid metamaterials; extending the framework to nonlinear responses remains for future work.
Read the full abstract ▾
All authors Minwoo Park, Junseo Park, Mingyu Lee, Hugon Lee, Hanbin Cho, Ikjin Lee, Seunghwa Ryu
Statistical Mechanics · Cross-listed from quant-ph
Unique temporal scaling dimension for quantum criticality in open systems weakly coupled to environment
Fan Zhong
Probing, understanding, predicting, and controlling the real-time dynamics of
quantum phase transitions in open systems are of pivotal importance to modern condensed matter physics, statistical physics, and
quantum computing, among others. Here it is argued that a distinct temporal renormalization-group
eigenvalue is needed for
quantum criticality in open systems weakly coupled to their finite-temperature environment. This new physics enables the formulation of a general scaling theory that can accurately account for the critical properties including the specific Kibble-Zurek scaling in such open
quantum systems. Remarkably, the critical exponents of time-related quantities are altered nonperturbatively regardless of how weak the coupling is, except for an Ohmic bath. Perspectives for future study are also discussed.
Read the full abstract ▾
Materials Science
Temperature dependence of charge-to-spin conversion in rhombohedral (110) bismuth thin film
K. Tatsuoka, N. Fukumoto, S. Sakamoto et al. (+7 more)
The amplitude of charge-to-
spin conversion, namely the
spin Hall effect (SHE), in bismuth (Bi) strongly depends on its
crystal orientation. The conversion efficiency at room temperature in rhombohedral (110) bismuth is notably large as expected from its large
spin-orbit interaction, and such a large SHE is ascribed to the large effective g-factor in bismuth [N. Fukumoto et al., Proc. Nat. Acad. Sci. 120, e2215030120 (2023)]. Despite the successful observation of the large conversion efficiency, a more detailed physical mechanism of the SHE in (110) bismuth is still elusive and under debate. In this work, we investigate the temperature dependence of charge-to-
spin conversion in an epitaxial Bi(110)/Ni
bilayer system using the second harmonic
Hall method, revealing that both
spin Hall conductivity and
spin diffusion length augment with decreasing temperature. This finding suggests that
spin scattering in (110) bismuth is dominated by the Elliott-Yafet mechanism, and the charge-to-
spin conversion is mainly attributed to skew scattering.
Read the full abstract ▾
All authors K. Tatsuoka, N. Fukumoto, S. Sakamoto, S. Miwa, Y. Fuseya, J. Fujimoto, R. Ohshima, J. Puebla, Y. Ando, M. Shiraishi
Materials Science
Electric field induced Berry curvature dipole in quasi-one-dimensional Bi$_4$I$_4$
Amiya Mondal and Awadhesh Narayan
The nonlinear
Hall effect in time-reversal symmetric materials offers a powerful probe into
quantum geometry. Here, we investigate the electric-field-tunable nonlinear
Hall response in few-layer $\text{Bi}_4\text{I}_4$ using comprehensive first-principles calculations across both its $\alpha$ and $\beta$ phases. Guided by
symmetry analysis, we track the
evolution of the Berry
curvature dipole (BCD) tensor from the monolayer to the
bilayer configuration under an out-of-plane electric field. While the monolayer features a highly rigid band structure and modest BCD tunability, the
bilayer architecture exhibits substantial field-induced band modifications, including a progressive Rashba splitting and eventual gap closure in the $\beta$ phase. Crucially, this field-tunability allows substantial enhancement of the BCD magnitude relative to the monolayer counterpart. Our findings establish quasi-one-dimensional bismuth halogenides as a promising platform for engineering nonlinear
Hall response.
Read the full abstract ▾
Soft Condensed Matter
Vectorial driving of multistable materials: singularities, pt-graphs, and non-generic paths
Colin M. Meulblok and Martin van Hecke
Describing and predicting the response of multistable materials to external driving is central to
memory formation, programmable metamaterials, soft robotics, and in-materia computing. While scalar driving is captured by transition graphs (t-graphs), vectorial driving produces path-dependent responses that require the recently introduced path-transition graphs (pt-graphs). In both cases, transitions are governed by singularities in the energy landscape: for scalar driving these correspond to saddle-node bifurcations, but for vectorial driving, higher-order singularities become important. Combining experiments on chain-like metamaterials with a minimal spring model, we investigate how higher-order singularities shape pt-graphs and the resulting path-dependent responses. We moreover discuss the role of non-generic driving paths through higher-order singularities, where the response is governed by spontaneous
symmetry breaking. Finally, we demonstrate how t-graphs emerge as the one-dimensional limit of pt-graphs, unifying scalar and vectorial driving within a common graph-based framework. These results establish a singularity-based approach to path-dependent responses and provide a foundation for designing multistable materials with programmable sequential functionality for smart sensing, soft robotics, and in-materia computation.
Read the full abstract ▾
Materials Science
A Generalized Frank-Bilby Equation for Interfaces in Crystalline Materials
Dongsong Tao, Luchan Zhang, David J. Srolovitz et al. (+2 more)
The classical Frank-Bilby equation (FBE) is commonly used to predict the structure of interfaces in crystalline materials in terms of interfacial dislocation networks. However, in general, the line defects in interfaces are disconnections, possessing both dislocation and step character, which are not captured by the classical FBE. As a result, the FBE cannot fully describe the structure of most interfaces of practical interest. To address this issue, we derive a generalized Frank-Bilby equation (GFBE) that explicitly incorporates both dislocation and step components of interfacial defects. We demonstrate its application to several representative interface systems.
Read the full abstract ▾
All authors Dongsong Tao, Luchan Zhang, David J. Srolovitz, Yang Xiang, Jian Han
Soft Condensed Matter
Molecular Dynamics-Derived Coloured Noise Mediates Anderson Localisation and Environment-Assisted Transport of Tryptophan Excitons in Tubulin
Chen Xin
The tryptophan residues in tubulin $\alpha\beta$-dimers form an ordered aromatic network that has been proposed to support
quantum exciton transport even under physiological environmental noise. Existing studies of this system mostly assume white-noise dephasing, but the statistical properties of the
protein-solvent bath coupled to tryptophan sites remain uncharacterised under physiological conditions. Here we characterise this fluctuation bath via all-atom molecular dynamics simulations of a solvated tubulin dimer at 310 K, combining high-frequency and long-time trajectories with 10 fs and 10 ps sampling intervals. The resulting autocorrelation of the site-energy fluctuations is tri-exponential, with three well-separated decay modes: sub-100-fs and picosecond fluctuations driven by water dynamics, and a nanosecond mode originating from
protein conformational rearrangements. All three modes fall deep within the non-Markovian regime. We further demonstrate that the slow
protein mode introduces strong quasi-static disorder, which results in Anderson localisation, while the two fast water modes frequently tune chromophore pairs through resonance, enabling environment-assisted
quantum transport (ENAQT). On the full eight-site network, the coloured-noise bath confines
excitons predominantly to strongly coupled proximal tryptophan pairs, in marked contrast to the more uniform delocalisation predicted by the standard white-noise Haken-Strobl model. Our workflow generalises to other pigment-
protein systems with solvent-exposed chromophores.
Read the full abstract ▾
Superconductivity
Strain-Tuned Nodal Superconductivity in the Charge-Ordered Kagome Metal CsV$_3$Sb$_5$
Yusuke Takeuchi, Akito Kobayashi, Saki Uchida et al. (+8 more)
The nature of the superconducting pairing
symmetry in the kagome metal CsV$_3$Sb$_5$ and its relationship with the charge density wave (CDW) order are central unresolved issues. Here, we investigate the
evolution of superconductivity in CsV$_3$Sb$_5$ under in-situ uniaxial pressure using $^{121}$Sb
nuclear quadrupole resonance (NQR). We find that tensile strain significantly enhances the superconducting transition temperature, $T_{\rm c}$, while the CDW remains unchanged, demonstrating that superconductivity can be tuned independently of the bulk charge order. At a tensile strain of $\varepsilon$ = +0.90%, the
nuclear spin-
lattice relaxation rate reveals a remarkable double transition: an upper transition at $T_{\rm c1}$ = 3.6 K to a nodal gap state, and a lower one at $T_{\rm c2}$ = 3.0 K characterized by a nodeless gap. These results evidence degenerate superconducting states with different gap
symmetry in the kagome metal at ambient pressure which split under strain. Our work demonstrates a high tunability of superconductivity by uniaxial pressure.
Read the full abstract ▾
All authors Yusuke Takeuchi, Akito Kobayashi, Saki Uchida, Takumi Nagao, Seigo Ogawa, Rui Zhou, Shinji Kawasaki, Fei Song, Hao Ni, Yong Zhao, Guo-qing Zheng
Materials Science
Tiling decomposition multiplicity predicts stability of GaN(0001) surface reconstructions
Tetsuji Kuboyama, Akira Kusaba, Karol Kawka et al. (+1 more)
The stable adatom configurations of a
semiconductor surface have traditionally been sought by sampling: density functional theory (DFT) energies steer a heuristic or
Bayesian search through a configuration space far too large to cover. Here we show that, for the GaN(0001)-$(6\times6)$ surface under the electron counting (EC) rule, the search can instead be posed as a discrete tiling problem and solved exhaustively. Enumerating all rhombus tilings of the surface
lattice, together with all EC-compatible adatom arrangements built on them, yields the complete catalog of 416,683 configurations at fixed stoichiometry (3 Ga adatoms and 18 H atoms), organized by
symmetry into 14 Ga placement classes. The number of tilings compatible with a given configuration, its tiling decomposition multiplicity $n_\mathrm{til}$, predicts stability. Within each class, the configuration maximizing $n_\mathrm{til}$ is the most stable. The rule holds strictly in 13 of the 14 classes; in the remaining class the minimum is itself among the highest-multiplicity configurations, with the $n_\mathrm{til}$-max configuration only 8.5 meV above it; this ordering is reproduced by independent DFT calculations, and the difference is negligible at growth temperature. Stability screening uses a machine-learning interatomic potential validated against 710 DFT-computed structures. The rule reduces the candidate set for first-principles evaluation from 416,683 to 24 configurations, all of which have been evaluated with DFT. Analysis of the rule identifies the local mechanism, the avoidance of adjacent bare surface sites, while the existence of a compatible tiling remains a separate requirement with an energy cost of its own. Enumeration thus provides what sampling cannot: a coverage guarantee, and a route to stable-structure prediction in which first-principles input enters only at the final ranking step.
Read the full abstract ▾
All authors Tetsuji Kuboyama, Akira Kusaba, Karol Kawka, Pawel Kempisty
Materials Science
Effect of annealing temperature on the structure and properties of co-sputtered Fe-Mn-Sn films near 2:1:1 ratio
Lance Griswold and Dipanjan Mazumdar
Research in recent years has focused on the thin-film synthesis of high-quality ternary
alloys, identified for their tunable properties and potential in spintronics (e.g., Heusler
alloys, Kagome magnets). In a previous study, we identified the conditions for stabilizing Fe$_2$MnSn, a Kagome magnet with a high Curie temperature and
magnetic anisotropy. However, ternary phases such as Fe$_2$MnSn are challenging to synthesize and stabilize within a narrow temperature window, as binary and elemental phases can also form during the growth process. To highlight these observations, we investigated the thin film phases in the Fe-Mn-Sn system near the 2:1:1 ratio as a function of annealing temperature, ranging from 400 to 700\degree C. The elemental Fe, Mn, and Sn targets were pre-calibrated to a close to 2:1:1 ratio and co-sputtered at room temperature, followed by annealing. Two binary hexagonal structures, Fe$_3$Sn$_2$ and Fe$_5$Sn$_3$, along with the elemental Fe phase, are stabilized between 400-550\degree C, but disappear at 580\degree C, where Fe$_2$MnSn is the only stable phase. Elemental Mn phase starts to appear starting from 600\degree C, and becomes dominant by 750\degree C. Electrical,
magnetic and magneto-optical properties are observed to correlate with the structural findings and the best properties are observed in the temperature range where Fe$_2$MnSn is the dominant phase. In general, our study highlights the difficulty in growing phase-pure ternary
alloys such as Fe$_2$MnSn, which is very strongly based on precise temperature conditions. We also observed significant disordered growth below 100 nm for Fe$_2$MnSn, implying poor thickness scaling behavior.
Read the full abstract ▾
Statistical Mechanics
Finite-time Scaling of the surface special transition in a 3D classical Heisenberg model
Dong-Xu Liu, Zhe Wang, Shuai Yin et al. (+1 more)
We investigate nonequilibrium driven dynamics across the special surface phase transition in the three-dimensional classical Heisenberg model with open boundaries, where tuning the surface coupling gives access to an extraordinary-log boundary critical state characterized by logarithmic, rather than power-law, decay of correlations. Using Monte Carlo simulations, we realize four driving protocols: temperature heating and cooling across the special transition, and surface-coupling ramps from the ordinary and extraordinary-log critical states into the special point. For temperature-driven protocols, the surface order parameter obeys a generalization of the finite-time scaling (FTS) and the Kibble-Zurek mechanism. The central finding emerges when the system is driven from the extraordinary-log critical state: the large-rate scaling relation acquires a logarithmic correction and takes the novel form $M^{2}_{s}\propto R^{(1+\eta_{s})/r_{s}}[\log(LR^{1/\eta_{s}})]^{-q}$ , where $R$ is the driving rate, $L$ the system size, $\eta_{s}$ the surface anomalous dimension, $r_{s}$ the scaling dimension of $R$, and $q$ the exponent governing the logarithmic boundary criticality. We demonstrate that this form follows from the general FTS framework by incorporating the logarithmic initial-state
memory, and we achieve excellent data collapse over a wide range of system sizes and driving rates. Our results establish that extraordinary-log initial states alter nonequilibrium critical scaling, extending boundary FTS beyond conventional power-law initial conditions.
Read the full abstract ▾
All authors Dong-Xu Liu, Zhe Wang, Shuai Yin, Zheng Yan
Materials Science
Neural-network-based reconstruction of spin and orbital angular momentum from X-ray magnetic circular dichroism spectra
Tetsuro Ueno
X-ray
magnetic circular dichroism (XMCD) is a powerful probe of element-specific
spin and orbital angular momentum. Conventional analyses based on sum rules, however, rely on integrated spectral intensities and can become insufficient when multiple parameters influence the spectral line shape. Here, we formulate XMCD analysis as an inverse problem and develop a neural-network (NN) based approach to reconstruct
spin and orbital angular momentum directly from full spectral line shapes. Using many-body multiplet calculations of Fe, Co, and Ni $L_{2,3}$-edge X-ray absorption spectra (XAS) and XMCD spectra as a physically well-defined training
dataset, we systematically vary key parameters including
crystal-field splitting,
spin–orbit coupling, and exchange field. The NN is trained to map spectral line shapes onto the expectation values of
spin and orbital angular momentm $\langle S_z \rangle$ and $\langle L_z \rangle$, and validated using strictly test-only data. The results demonstrate accurate and unbiased reconstruction, establishing a proof of concept for data-driven inverse reconstruction from XAS and XMCD spectra. These findings show that exploiting the full XAS and XMCD line shapes provide access to information beyond conventional sum-rule analyses while remaining consistent with established theoretical frameworks.
Read the full abstract ▾
Strongly Correlated Electrons
Generalized Keldysh formalism for nonequilibrium correlation functions and its application to fluctuation dynamics
Ken Inayoshi, Hiroshi Shinaoka and Yuta Murakami
Recent advances in time-resolved spectroscopies provide increasing access to collective dynamics in correlated
quantum materials. However, computing the corresponding nonequilibrium two-particle correlation functions remains a major challenge. Here, by introducing a contour-dependent virtual probe field within the generalized Keldysh formalism, we propose an approach that computes such correlation functions with the vertex corrections essential for describing collective dynamics. In particular, we introduce a linear integral equation that computes the correlation functions without explicitly constructing the four-time vertex kernel, and develop its
matrix-free Krylov solver based on quantics tensor trains. Combining our method with nonequilibrium dynamical mean-field theory, we show that the fluctuation dynamics of the order parameter in a nonequilibrium
symmetry-broken state depends significantly on whether vertex corrections are included, and that the fluctuation and its decay time grow near the nonthermal critical point. Our approach thus provides a practical route for evaluating nonequilibrium correlation functions, which are emerging as key observables for characterizing states far from
equilibrium.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Spectroscopy of low-lying valley states in hot Si/SiGe quantum dots
Connor Nasseraddin, Heun Mo Yoo, Tanner M. Janda et al. (+1 more)
The presence of low-lying valley states in Si may hinder the development of large-scale
spin-based
quantum processors. Rapid prototyping of novel Si/SiGe
heterostructures and gate stacks will be central to identifying pathways that increase the valley splitting. We compare the performance of pulsed-gate spectroscopy (PGS) and detuning axis spectroscopy (DAPS) at temperatures up to 700 mK. We find that DAPS outperforms PGS, with DAPS resolving valley splittings as small as ~86 $\mu$eV, while the energy resolution of PGS is only ~210~$\mu$eV. Our work demonstrates that DAPS can be used to efficiently extract valley splittings at elevated temperatures in high throughput cryostats.
Read the full abstract ▾
All authors Connor Nasseraddin, Heun Mo Yoo, Tanner M. Janda, Jason R. Petta
Materials Science
Telecom-band Chiral Light Detection through Hidden Giant Third-Order Nonlinear Circular Dichroism in Two-dimensional Halide Perovskite
Yuki Takahashi, Daichi Okada, Koshi Oi et al. (+5 more)
Chiral nonlinear optical (NLO) responses enable efficient discrimination of circularly polarized light (CPL) and are attracting increasing interest for optical and optoelectronic technologies. However, studies on NLO properties in
chiral materials have largely focused on second-order NLO processes, while the role of chirality in third-order NLO processes remains poorly explored. Here, we demonstrate telecom-band CPL detection by third harmonic generation circular dichroism (THG-CD) in the
chiral two-dimensional perovskite (R/S-MBACl)2PbI4 and uncover a
giant hidden THG-CD anisotropy that is accessible via polarization-resolved detection. Polarization-resolved THG measurements reveal that opposite
chiral NLO responses emerge in orthogonal THG polarization channels. Therefore, these
chiral anisotropic contributions largely cancel each other in the total-THG signal detection, leading to underestimation of the THG-CD dissymmetry in conventional evaluations based on total-THG intensity. By separating these hidden
chiral contributions, we observe exceptionally large dissymmetry factors exceeding 1.9 and achieve selective extraction of
chiral NLO responses with opposite handedness, without any structural
chiral inversion. These findings highlight the importance of polarization-resolved analysis for evaluating more accurate
chiral NLO responses inherent to the material and provide a promising platform for optical information processing, encryption, and anti-counterfeiting technologies at technologically relevant telecommunication wavelengths.
Read the full abstract ▾
All authors Yuki Takahashi, Daichi Okada, Koshi Oi, Kazuki Mitamura, Takahiko Endo, Yasumitsu Miyata, Taishi Takenobu, Kenichi Yamashita