Through systematic experimental and theoretical studies of layer-thickness-dependent absorption in semiconducting ${\mathrm{MoSe}}_2$ and ${\mathrm{WS}}_2$ across the visible to near-infrared spectral range, we demonstrate a universal absorption behavior in solids at nanoscale thicknesses. With increasing thickness, a nonmonotonic evolution of absorption integrated over the measured spectral region is revealed which is accompanied by pronounced oscillatory features. This shows a strong deviation from the expected Beer-Lambert law. Below 10 nm, we observe a sharp anomalous increase in absorption, with deviations from Beer's law exceeding 50% in layered semiconductors. Our conclusions hold irrespective of the presence of any optical resonances such as excitons or plasmons within the spectral window. The observed behavior has origins in the electromagnetic interference effects taking place between the two surfaces of the thin crystals. The present work on two-dimensional (2D) semiconductors is extendable to all kinds of solids such as conventional semiconductors (e.g., Si, GaAs, GaN, InP), (semi)metals (e.g., Al, Ag, Au, c-HOPG), and 2D magnetic materials (e.g., CrSBr and ${\mathrm{NiPS}}_3$). Our results provide fundamental insights into light-matter interactions in solids at the nanoscale and are vital for optimally designing next-generation absorption-based flexible optoelectronic devices.

The effect of rare system-wide resonances in the many-body localization (MBL) transition has recently attracted significant attention. They are expected to play a prominent role in the stability of the MBL phase, prompting the development of new theoretical frameworks to properly account for their statistical weight. We employ a method based on an analogy with mean-field disordered glassy systems to characterize the statistics of transmission amplitudes between distant many-body configurations in Hilbert space and apply it to the random-field XXZ spin chain. By introducing a Lagrange multiplier, which formally plays the role of an effective temperature controlling the influence of extreme outliers in the heavy-tailed distribution of propagators, we identify three distinct regimes: (i) an ergodic phase with uniform spreading in Hilbert space, (ii) an intermediate regime where delocalization is driven by rare, disorder-dependent long-range resonances, and (iii) a robust MBL phase where such resonances cannot destabilize localization. We derive a finite-size phase diagram in the disorder–interaction plane, both in the spin and in the Anderson basis, that quantitatively agrees with recent numerical results based on real-space spin-spin correlation functions. We further demonstrate that even infinitesimal interactions can destroy the Anderson insulator at finite disorder, with the critical disorder remaining finite down to small interaction strengths. By visualizing resonant transmission pathways on the Hilbert-space graph, we provide a complementary perspective to real-space and spectral probes, revealing how the destabilization of the MBL phase at finite sizes stems from the emergence of resonant paths that become progressively rarer and shorter-ranged deep in the localized phase.

Previous investigations of dynamical quantum phase transition (DQPT) have predominantly focused on sudden quench protocols. In this work, we systematically explore the fate of DQPT from the sudden to the slow quench regime. We establish that DQPT remains robust under slow quenching when the protocol crosses an equilibrium quantum phase transition. Conversely, we show that accidental DQPTs—which occur when the pre- and postquench Hamiltonians reside in the same equilibrium phase—can be filtered out in the slow quench limit. This demonstrates that slow quenches can reveal the intrinsic connection between DQPT and equilibrium quantum phase transitions, thereby enabling DQPT to serve as a dynamical probe for identifying equilibrium quantum critical points. We illustrate these findings with examples from the XY chain, the Aubry-André model, and the trimer Su-Schrieffer-Heeger model.

We propose a strategy to enhance dielectric permittivity by tuning local electronic structures, exemplified by Nb-doped rutile-type $\mathrm{Ti}{\mathrm{O}}_2$. Substituting only 0.5% of ${\mathrm{Ti}}^{4+}$ with $\mathrm{N}{\mathrm{b}}^{5+}$ increases the relative permittivity by ∼1200—fivefold higher than that of pristine $\mathrm{Ti}{\mathrm{O}}_2$—while maintaining low dielectric loss (tan δ ∼ 0.02) at cryogenic temperatures. First-principles calculations reveal that excess electrons introduced by Nb substitution localize between Nb and adjacent Ti ions, forming molecular polarons with intrinsic electric dipole moments. These polarons undergo quantum tunneling–assisted flip-flop hopping between their first-nearest-neighbor Ti sites, allowing field-induced dipole reorientation even at 4.2 K. This mechanism explains the persistence of high permittivity at cryogenic temperatures, where classical hopping and Maxwell–Wagner–Sillars effects become negligible, and provides a microscopic explanation for the saturation observed at higher Nb concentrations because of Nb–Nb dimer formation and polaron trapping. Our findings establish a design framework for quantum-enhanced dielectrics based on local correlations and tunneling dynamics in simple oxides.

The structural, vibrational, and optical properties of ${\mathrm{Rb}}_2{\mathrm{TeBr}}_6$ have been investigated under high pressure using synchrotron x-ray diffraction, Raman spectroscopy, photoluminescence (PL), and optical absorption measurements. At ambient conditions, ${\mathrm{Rb}}_2{\mathrm{TeBr}}_6$ crystallizes in the cubic Fm-3m structure, which remains stable below 8.0 GPa. Our x-ray diffraction analyses reveal that in the parent cubic phase, subtle interoctahedral rotations develop, producing a localized deviation from the ideal cubic framework. This local asymmetry facilitates radiative recombination, leading to a pronounced enhancement of PL intensity up to 2.4 GPa. The gradual increase in phonon lifetime till about the same pressure as observed in Raman measurements corroborates an electronic transition. Above this pressure point, broadening in the widths of the Raman modes indicates an increase in the phonon scattering processes, leading to enhancement of nonradiative relaxation channels resulting in gradual PL quenching. Additionally, the PL intensity increases upon the application of a weak external magnetic field. A structural transition to the orthorhombic Pnnm phase occurs at around 8.0 GPa, followed by a monoclinic $\mathrm{P}{2}_1/m$ phase at around 10.7 GPa, and eventual amorphization at 25.5 GPa. Optical absorption spectra reveal continuous narrowing of the band gap upon compression. These findings demonstrate the strong coupling among lattice dynamics, electronic structure, and optical response in ${\mathrm{Rb}}_2{\mathrm{TeBr}}_6$, underscoring its potential as a pressure-tunable optoelectronic material.

Nonreciprocal many-body systems have been predicted to support various novel phenomena of heat transfer. Persistent heat current represents striking heat flow at thermal equilibrium among at least three nonreciprocal bodies. However, the directionality of the persistent heat current, defined as the relative contrast between the heat flows between two bodies in opposite directions, is limited. Here, we introduce a general strategy to enhance the directionality by using inhomogeneous magnetization. Using fluctuational electrodynamics, we numerically show that among four magneto-optical nanospheres in inhomogeneous magnetic fields, the directionality can reach $680\%$. The calculation agrees with coupled mode theory. We further show that the strategy also applies to nonreciprocal systems consisting of magnetic Weyl semimetals. We show that for a system consisting of four magnetic Weyl semimetal nanospheres in inhomogeneous magnetization, the directionality can reach $717\%$, even without an external magnetic field. The directionality achieved using inhomogeneous magnetization is over 1 order of magnitude higher than in prior studies. Our strategy can be useful for enhancing nonreciprocal radiative heat transfer for thermal management and energy conversion.

Altermagnets have zero net magnetization and nonrelativistic spin splitting, which is ideal for spintronic applications. The control of the spin state is of crucial importance. Here, the laser-induced spin dynamics in an altermagnet/metal heterostructure has been investigated using the real-time time-dependent density functional theory. The laser irradiation induces the unbalanced demagnetizations of the opposite-spin sublattices, resulting in an ultrafast magnetic order transition of the altermagnet. After irradiated by laser pulses with different fluences and polarizations, the altermagnet can transiently turn to ferrimagnetic, ferromagnetic, or nonmagnetic states. Simultaneously, the spins are injected into the nonmagnetic substrate with a negligible charge injection. Those phenomena are caused by the intersite electron transfers of both spin channels. As the two opposite-spin sublattices can be selectively excited according to the rotational symmetry of the altermagnet, the direction of the magnetization of the altermagnet and the injected spin component can be controlled by using different linearly polarized laser pulses. The research demonstrates the laser-induced controllable magnetic order switching and spin injection of the altermagnetic system, which paves the way for high-speed spintronic applications.

Despite extensive research, the precise spin Hamiltonian of the van der Waals antiferromagnet ${\mathrm{NiPS}}_3$—which hosts a zigzag-ordered ground state—remains debated. While consensus has emerged on ferromagnetic nearest-neighbor ($J_1$) and antiferromagnetic third-nearest-neighbor ($J_3$) Heisenberg interactions, recent studies suggest that a biquadratic ($B$) exchange term may also play a role, though its estimated magnitude varies widely. To address this controversy, we perform density functional theory calculations and extract a positive biquadratic interaction with $B/J_3\approx 0.44$. Within the minimal $J_1\text{−}{J}_3\text{−}B$ model, we show that these parameters naturally stabilize zigzag ordering using minimally augmented spin-wave theory. Density-matrix renormalization group calculations further validate our extracted parameters as a reasonable description of the ground state. Although fully resolving the spin Hamiltonian of ${\mathrm{NiPS}}_3$ requires further investigation, our findings provide insights into its biquadratic interaction.

Although neither hard-core bosons nor fermions can occupy the same single-site state, they still obey different statistics, resulting in distinct many-particle quantum states, such as condensate states versus Fermi-liquid states. However, when only pair states are considered, the two can take the same form, since a local hard-core Bose pair and a Fermi pair obey the same statistics. In this work we demonstrate this by studying both Fermi and Bose extended Hubbard ladders, which can be realized experimentally in synthetic atomic ladders. A set of exact condensate-pair eigenstates for the Fermi ladder is constructed under SU(2) symmetry and can then be obtained by the spectrum generating algebra. The corresponding hard-core boson counterpart can be simply obtained by replacing fermionic operators with hard-core bosonic ones. Nevertheless, the boson-pair eigenstates are associated not with symmetry but with the restricted spectrum generating algebra. We also investigate the effect of next-nearest-neighbor hopping on the condensate states through numerical simulations of the dynamic response. The conclusions can be extended to a two-layer system. Our result reveals not only the resemblance of fermions to hard-core bosons, but also a possible mechanism of Hilbert-space fragmentation.

Topological quantum matter represents a flexible playground to engineer unconventional excitations. While noninteracting topological single-particle systems have been studied in detail, topology in quantum many-body systems remains an open problem. Specifically, in the quantum many-body limit, one of the challenges lies in the computational complexity of obtaining the many-body ground state and its many-body topological invariant. While algorithms to compute ground states with quantum computers have been heavily investigated, algorithms to compute topological invariants in a quantum computer are still under active development. Here we demonstrate a quantum circuit to compute the many-body topological invariant of a second-order topological quantum magnet encoded in qubits. Our algorithm relies on a quantum circuit adiabatic evolution in transverse paths in parameter space, and we uncover hidden topological invariants depending on the traversed path. Our work puts forward an algorithm to leverage quantum computers to characterize many-body topological quantum matter.

We establish twisted ${\mathrm{SnSe}}_2$ as a tunable platform for simulating dimension-dependent correlated physics, distinct from conventional K-valley moiré systems. By constructing interacting Wannier models, we show that the stacking configuration dictates the effective lattice geometry. In AA-stacked bilayers, a momentum-space nonsymmorphic symmetry constrains the single-particle hopping within each valley to be effectively one-dimensional while still allowing fully two-dimensional interactions, thereby giving rise to an effective quasi-one-dimensional system. This dimensional reduction stabilizes exotic phases including dimerized states with finite residual entropy, valence bond solids, and quantum paramagnetism. Conversely, AB stacking maps to a frustrated Kagome lattice; here, strong interactions drive the emergence of a classical spin liquid. The high tunability of this moiré system, which allows control over both the filling and interaction strength (via twist angle), renders twisted ${\mathrm{SnSe}}_2$ a versatile platform for realizing a wide range of exotic correlated quantum phases.

The Universal Operator Growth Hypothesis formulates the time evolution of operators through Lanczos coefficients. In practice, however, numerical instability and memory cost limit the number of coefficients that can be exactly computed. In response to these challenges, the standard approach relies on fitting early coefficients to asymptotic forms, but such procedures can miss subleading, history-dependent structures in the coefficients that subsequently affect reconstructed observables. In this work, we treat the Lanczos coefficients as a causal time sequence and introduce a transformer-based model to autoregressively predict future Lanczos coefficients from short prefixes. For classical and quantum chaotic systems, our model outperforms asymptotic fits in both coefficient extrapolation and physical observable reconstruction, and achieves an order-of-magnitude reduction in error. The model also accurately extrapolates coefficients in integrable regimes, where no universal asymptotic fit exists. Remarkably, our model transfers across system sizes: it can be trained on smaller systems and then be used to extrapolate coefficients on a larger system without retraining. By probing the learned attention patterns and performing targeted attention ablations, we identify portions of the coefficient history that are most influential for accurate forecasts. Our results demonstrate that modern sequence models can serve as practical surrogates for probing operator dynamics deep in Krylov space, where brute-force Lanczos iteration can be computationally prohibitive.

We report the growth of high-quality single crystals of the magnetic topological semimetal EuAuBi using a Pb-flux method, which effectively suppresses the formation of secondary ${\mathrm{Au}}_2\mathrm{Bi}$ impurity phases that were prevalent in the previously reported Bi-flux grown crystals. This growth optimization enables reliable investigation of the intrinsic physical properties of EuAuBi. Importantly, Pb flux growth stabilizes $c$-axis-oriented single crystals, enabling Hall measurements in a previously unexplored geometry. In this configuration ($I\parallel c,B\perp c$), a finite residual Hall contribution, consistent with topological Hall signal, emerges below the antiferromagnetic ordering temperature and within particular magnetic field ranges. This Hall contribution coincides with the metamagnetic transitions, anomalies in magnetoresistance, and an additional feature in field-dependent specific heat, indicating strong coupling between the electronic transport and field-induced magnetic reconstructions. Consequently, these findings underscore the significance of crystal orientation in uncovering topological transport signatures in magnetic semimetals such as EuAuBi.

We present a simple methodology to compute the anomalous Hall conductivity (AHC) as a function of the canting angles in ferromagnets and altermagnets, starting from a nonmagnetic Hamiltonian obtained from first-principles calculations that preserves the full symmetry of the crystal structure. Magnetism is introduced by including on-site spin splitting, spin-orbit coupling, and spin-canting angles. As a representative material, we study ${\mathrm{SrRuO}}_3$, which supports spin canting and exhibits a sign change of the AHC. In the ferromagnetic phase, the low-energy AHC is found to be close to zero at the Fermi level, in agreement with experimental observations. We show that the dependence of the AHC on the relevant physical parameters is most pronounced in the central region of the electronic bandwidth. We determine the symmetry-allowed components of the AHC for different magnetic orders in the large family of transition-metal perovskite ${AB\mathrm{O}}_3$ compounds with space group 62, including the spontaneous in-plane anomalous Hall effect. Within density functional theory, we evaluate the range of spin-canting angles in ${\mathrm{SrRuO}}_3$ and demonstrate that it is suppressed as electronic correlations increase. By analyzing the AHC as a function of the canting angle, we find that the collinear magnetic configurations contribute most to the AHC, while spin canting plays a secondary role in determining its magnitude in noncollinear ferromagnets and altermagnets. However, canting can become relevant and induce a sign change of the AHC when the collinear magnetic state exhibits an AHC close to zero. Finally, we investigate the locations of Weyl points in the Brillouin zone and their evolution as a function of the canting angle.

We investigate spin-wave propagation in magnetic insulators in the presence of lattice dislocations. Within a continuum magnetoelastic framework, we show that the strain fields generated by dislocations induce equilibrium magnetic textures. The morphology of these textures depends sensitively on the dislocation type and acts as a localized scattering potential for spin-wave excitations. As a result, the scattering response exhibits pronounced asymmetries and interference effects governed by the magnetoelastic coupling and the dislocation type. By combining numerical simulations with analytical scattering theory, we compute differential cross sections and frequency-dependent transmission coefficients. Furthermore, analysis of the effective potential landscape reveals that the defect forms a barrier that modulates spin-wave transport and, crucially, breaks the intrinsic reflectionless nature of magnetic domain walls. Our findings identify lattice dislocations as tunable scattering centers, opening new avenues for defect engineering in magnonic devices.

Sodium niobite $({\mathrm{NaNbO}}_3, \mathrm{NNO})$ is a technologically important material featuring a complex phase diagram with multiple, intricately coupled structural phases. While the structural complexity of NNO has inspired extensive experimental and theoretical investigations, the finite temperature behavior of lattice excitations and their role in temperature-induced phase transitions remain poorly understood. Here, we bridge this gap by studying the spectra of collective lattice vibrations using a first-principle-based effective Hamiltonian model. Our results reveal that the two highest-in-temperature structural transitions are driven by condensation of softening phonon modes. Such maximum and next-maximum temperature transitions give rise to an in-phase and antiphase oxygen octahedral tilting, respectively. Moreover, we find that in the vicinity of the highest transition temperature, paraelectric NNO features dispersionless transverse optic (TO) modes at the $\text{R}-\text{M}$ edges of the Brillouin zone, with the corresponding flat bands rigidly softening upon cooling. Our results thereby reveal a highly degenerate manifold of competing antipolar states and antiferrodistortive instabilities.

Continuum dislocation dynamics (CDD) has become the state-of-the-art theoretical approach for mesoscale dislocation plasticity of metals. Within this approach, there are multiple CDD theories that can all be derived from the principles of statistical mechanics. In these theories, density-based measures are used to represent dislocation lines. Establishing these density measures requires some level of coarse-graining, with the result of losing track of some parts of the dislocation population due to cancellation in the tangent vectors of unaligned dislocations. The leading CDD theories either treat dislocations as nearly parallel, as in the line bundle approach [J. P. Anderson et al., Phys. Rev. B 109, 174103 (2024)], or distributed locally over orientation space [T. Hochrainer, Philos. Mag. 95, 1321 (2015)]. The difference between these theories is a matter of the spatial resolution at which the definition of the relevant dislocation density field holds: for fine resolutions, single dislocations are resolved, and there is no cancellation; for coarse resolutions, whole dislocation loops could contribute at a single point, and there is complete cancellation. In the current work, a formulation of the resolution-dependent transition between these limits is presented in terms of the statistics of dislocation line orientation fluctuations about a local average line direction. From this formulation, a study of the orientation fluctuation behavior in intermediate resolution regimes is conducted. The fluctuation distributions are found to be roughly Cauchy in shape and broaden with increased coarse-graining length. Two possible closure equations for truncating the moment sequence of the fluctuation distributions relating the two theories mentioned above are evaluated from data, the newly introduced line bundle closure, and the previous standard maximum entropy closure relations. The line bundle closure relation is shown to be accurate for coarse-graining lengths up to half the dislocation spacing, and the maximum entropy closure is found to poorly agree with the data at all coarse-graining lengths.

Multistable mechanical metamaterials enable programmable transitions between discrete stable states through propagating kink transition waves. Yet controlling these kinks typically requires local actuation or high-energy deformation, limiting scalability. Here we demonstrate a universal strategy for pinning and depinning transition waves using local defects and boundary phonon excitations. Inspired by phonon-dislocation interactions in crystalline solids, we use pairs of phonons that form a beating envelope resonant with the pinned kink's translational mode, which lies within a phononic band gap. This resonant coupling efficiently transfers energy to the kink, allowing it to overcome defect barriers and propagate across impurities. The proposed mechanism enables application of these systems as information processing units in mechanical computing, namely as scalable and more robust mechanical memory.