Papers

Detector cost remains a barrier to the widespread adoption of mid-wave infrared (3-5 micron) technology. PbSe, an inexpensive narrow band gap IV-VI semiconductor that has been used since the early 1940s, delivers high performance for infrared detection despite the abundance of grain boundaries in polycrystalline films. Epitaxial growth, however, could provide superior crystalline quality and interfaces, but suitable substrates remain limited for PbSe. Recent PbSe heteroepitaxy has focused primarily on III-V, II-VI and group-IV substrates that each offer a comparatively narrow range of lattice-matched alloys for heterostructure engineering. Here we show that InP-based heteroepitaxy provides access to a broader materials platform while limiting the lattice mismatch with PbSe to approximately 4%. We grow 150-nm thick PbSe films by molecular beam epitaxy on 200-nm thick In0.53Ga0.47As and In0.52Al0.48As buffers on (001) InP substrates. Reflection high-energy electron diffraction and X-ray diffraction show (001)-oriented rock-salt PbSe with an out-of-plane lattice constant of 6.12 Angstrom on both buffers. Photoluminescence (PL) is observed from room-temperature down to 12 K and the peak wavelength red-shifts from 3.7 to 5.0 microns. Under identical measurement conditions, the room-temperature peak PL intensities from films on In0.53Ga0.47As and In0.52Al0.48As are approximately 1.9x and 1.3x that of a PbSe on GaAs substrate reference, respectively. These results establish an InP-compatible platform for integrating narrow band-gap PbSe with a broad range of ternary and quaternary III-V alloys, including, for example, structures in which In0.53Ga0.47As serves as both a short-wave infrared absorber and a template for PbSe growth.

Two-dimensional metal-organic frameworks (2D MOFs), with diverse topological architectures, provide a powerful platform for exploring unconventional electronic and lattice-dynamical responses. Yet their structural diversity remains fundamentally constrained by the fixed geometry of high-symmetry ligands. Here, we introduce an encoded asymmetric ligand, benzo[b]triphenylene-2,3,6,7,11,12-hexaol (BTH), for metal-selective topological assembly. By integrating multi-site coordination fields with sterically differentiated environments, BTH exhibits distinct topological programmability: different divalent metal ions direct divergent framework architectures. Specifically, coordination of BTH with divalent Cu(II) and Zn(II) ions assembles Cu-BTH-MOF with a dual-mode hexagonal pore topology and Zn-BTH-MOF with uniform hexagonal channels, respectively, as supported by PXRD Pawley refinement, structural simulations, and pore-size distribution analysis. Furthermore, this topological divergence is accompanied by a significant divergence in charge-transport properties, with Cu-BTH-MOF reaching an electrical conductivity of 1.186 x 10-3 S cm-1, more than six orders of magnitude higher than that of Zn-BTH-MOF (3.38 x 10-10 S cm-1). This work establishes ligand desymmetrization as a programmable strategy for metal-selective topological diversification in 2D MOFs.

Although minimalist models for patchy attractive particles have revealed powerful design rules for how particle valence directs colloidal assembly, less work has focused on comparably simple models of reversible, network-forming star polymers. Here, we use relative-entropy coarse-graining and simulation results from finer-resolution bead–spring star polymers to generate 5-bead models of dynamic, end-associating four-armed poly(ethylene glycol) macromers. Our results comparing structural correlations, network connectivity, and phase behavior of the coarse- and fine-grained models provide insight into how the accuracy and transferability of the coarse-grained models depend on the state point chosen for coarse-graining. The results also reveal intrinsic trade-offs between reducing degrees of freedom and expanding the range of effective interactions in coarse-graining that impact the total number of pairwise interactions in the resulting model, with implications for its computational efficiency.

Nonreciprocal interactions fundamentally alter energy transport by breaking the symmetry between forward and backward responses. Here, we uncover an exact transport structure for a one-dimensional harmonic chain with asymmetric nearest-neighbor couplings. Using a Green-function approach, we demonstrate that the direction of heat transport is determined not solely by the temperature bias, but by its competition with an effective directional asymmetry. This competition can reverse the direction of heat flow, enabling cold-to-hot transport. We further show that nonreciprocity introduces an additional power channel associated with the antisymmetric sector of the interaction, leading to a generalized steady-state energy balance involving two reservoir heat currents and a nonreciprocal power current. At the fluctuation level, the heat exchanges with the two reservoirs constitute correlated yet distinct stochastic currents, whose joint scaled cumulant generating function obeys an exact Gallavotti-Cohen symmetry. Together, these results establish a unified energetic and fluctuation framework for nonreciprocal heat transport and demonstrate that directional interactions can serve as an active resource for controlling nonequilibrium energy flows.

Understanding how thermal fluctuations modify or suppress quantum-enhanced sensing is a central problem in quantum metrology. Closely related questions arise in quantum thermodynamics, particularly regarding the relation between the work induced by a signal and the information acquired by a sensor. Here, we establish general relations among the sensitivity of thermal quantum states, as quantified by different quantum Fisher information metrics, their temperature dependence, and the work induced by a unitary signal. We further show that, at high temperature, all monotone QFI metrics coincide to leading order with a universal quantity that can be expressed as the variance of a simple observable and itself defines a lesser-known QFI metric. This emergent uniqueness is reminiscent of the uniqueness of classical Fisher information in information geometry. In continuous-variable systems, the infinite-temperature limit is finite and generically non-zero for quadratic Gaussian signals, while it diverges for higher-degree signals. Remarkably, for any purely quadratic signal generator, the infinite-temperature QFI is at least twice the zero-temperature SLD QFI or, equivalently, at least eight times the ground-state variance of the generator. Consequently, the Cramér–Rao lower bound on the estimator variance is reduced by at least a factor of two. We illustrate these results using harmonic chains of bosonic modes relevant to trapped-ion platforms and quantum field-theoretic models.

We present a theoretical study focused on the influence of Coulomb interactions on thermoelectric properties of molecular junctions assuming that electron transport is strongly affected by thermalized phonon modes in the molecular ambient. It is shown that the combined effect of Coulomb interactions between electrons on the molecular states and the reorganization processes in the ambient may significantly affect both Seebeck coefficient and the power factor. Specifically, we show that electron-electron interactions may counter-balance the effect of the ambient molecules reorganizations resulting in qualitative changes in the behavior of both zero-bias conductance and thermopower.

Ionic liquids (ILs) exhibit supercooled liquids behavior even above room temperature and the Stokes-Einstein (SE) relation is often considered to be invalid in ILs as that in supercooled liquids. However, the conclusion is usually drawn based on some variants of SE relation. In this work, we have systematically investigated the validity of the Stokes-Einstein relation in ILs by performing molecular dynamics simulations of coarse-grained IL within the temperature range of 400-800 K. Both the original SE formulation, and two commonly employed variants, were examined to assess their applicability and consistency. These three formulas yield distinctly different results, indicating that the two variants are not reliable substitutes for the original SE relation. The inconsistency suggests the fact that the r in Stokes law varies with conditions. The breakdown arises from the ion correlations introduced by the strong electrostatic interactions. This proposition is further confirmed by simulations.

Spatiotemporal fluctuations across multiple scales govern and characterize the emergent properties, phase boundaries, and low-energy excitations of strongly correlated matter. However, capturing these dynamics has remained a major experimental challenge, as conventional probes typically offer either high spatial or temporal resolution, but not both simultaneously. Here, we leverage high-fidelity wide-field imaging of dense diamond nitrogen vacancy center ensembles to measure the momentum and frequency power spectral density of magnetic fluctuations. To access spatial wavevectors below the diffraction limit, we tune the sensing volume continuously through optical depletion. This approach enables study of equilibrium and driven fluctuations across three orders of magnitude in spatial scale and tunable frequency bands, providing a direct means to map low-energy, long-wavelength fluctuations in correlated systems.

Hybrid organic-inorganic perovskite heterostructures are emerging platforms for energy conversion and optoelectronic devices, yet the effects of composition and surface terminations on band alignment remain poorly understood. Here, using high-throughput first-principles calculations, we systematically reveal the effect of composition and surface termination on the band alignment of 820 heterostructures formed between poly(3-hexylthiophene) (P3HT) variants and conventional and mixed-cation metal halide perovskites. Band edge analysis predicts concentration dependent band alignments, with most Pb and Sn based perovskites exhibiting Type II and III behavior while mixed-cation CsMASnBr3 uniquely forms Type-I junctions with all P3HT variants. Explicit interface calculations reveal that surface termination can reverse the predicted alignment in conventional tin perovskites, while the mixed cation perovskite preserves Type-I alignment with P3HT regardless of termination. Despite negligible charge transfer, termination dependent band offsets produce markedly different carrier confinement, establishing design principles for engineering P3HT/perovskite interfaces.

In Euclidean space, universality classes of Anderson transitions are primarily determined by symmetry and spatial dimensionality. Here, we present evidence for a geometry-controlled universality class of non-Hermitian Anderson transitions on hyperbolic-like lattices. In this setting, critical behavior is influenced by the large-scale hyperbolic geometry, characterized by negative curvature, exponential volume growth, and a non-Euclidean notion of spatial scaling. Finite-size scaling of participation ratios across several distinct \( \{p,q\} \) tilings reveals one-parameter scaling collapses with a common critical exponent \( \nu\simeq1 \) within numerical accuracy. A complementary phenomenological coarse-grained Landau-Ginzburg analysis shows how exponential correlation-volume growth suppresses critical fluctuations, offering a rationale for the observed mean-field-like scaling. Our results suggest that spatial curvature can act as an additional organizing principle for Anderson-transition universality beyond the conventional dimensionality- and symmetry-based classification.

The stabilizer Rényi entropy is a quantitative measure of non-stabilizerness, or magic, and has typically been found to scale extensively with system size $N$ (i.e., $\Theta(N)$) for a variety of many-body quantum states. In this note, we study the stabilizer Rényi entropy of the ground state of the spin-$\frac{1}{2}$ Dyck-Fredkin chain and its $t$-deformation, a local frustration-free model with unusual spectral-gap scaling. Exploiting the combinatorial structure, we carry out numerically exact finite-size calculations, which indicate asymptotic behavior depending on $t$: $\Theta(N)$ for $t<1$, $\Theta(\log N)$ at $t=1$, and $\Theta(1)$ for $t>1$. The scaling at $t=1$ could be another manifestation of the unconventional criticality of the model, while the contrast with the behavior of the entanglement entropy suggests that non-stabilizerness might provide a new window into quantum many-body systems.

We present a transferable graph neural network (GNN) surrogate framework for molecular dynamics (MD) that directly predicts atomic displacements and propagates atomistic configurations without explicit force evaluation or numerical time integration. The central objective of this work is to establish whether a common GNN formulation can represent atomic dynamics across materials with fundamentally different crystal symmetries and coordination environments. The same network architecture, feature representation, graph construction, and training protocol are applied without symmetry-specific modification to face-centered cubic (FCC) aluminum, body-centered cubic (BCC) iron, and hexagonal close-packed (HCP) magnesium. Across these distinct elemental and crystallographic systems, the framework achieves position-prediction errors on the order of 10^-4 Angstrom^2 and supports stable autoregressive propagation to nanosecond time scales. The predicted trajectories preserve thermodynamic stability, characteristic coordination-shell structure in the radial distribution functions, and temperature-dependent mean-squared-displacement behavior. In particular, the framework captures the closely spaced coordination shells of BCC iron and the anisotropic coordination environment of HCP magnesium without introducing lattice-specific representations. These results demonstrate that direct GNN-based atomic propagation can be formulated as a transferable framework across different elements, lattice symmetries, and coordination geometries, providing a pathway toward generalizable surrogate models for accelerated molecular dynamics.

Disordered hyperuniformity spans twenty-five orders of magnitude, from the microscopic world of soft and condensed matter to the distribution of matter in the universe. We introduce a free-energy functional with no adjustable coupling, a phase-field-crystal ordering term and a Newtonian tail, and show that its two kinetic limits generate two of these structures. Under conserved overdamped dynamics it arrests in a bicontinuous labyrinth of the kind found in confined fluids, block copolymers, active matter and vegetation patterns, which is a class III disordered hyperuniform state; under inertial dynamics in an expanding background it generates a cosmic web whose tidal skeleton matches that of gravity alone to within $0.03$ in every morphological class. In both limits the suppressed long-wavelength fluctuations are inherited from the initial condition rather than made by the dynamics: the large-scale exponent of the arrested state equals the primordial one, and gravity rescales the infrared spectrum by the linear growth factor to better than one per cent over a factor $1363$ of growth. The two sectors are continuously connected, and their distance is measurable: once the ordering modulation saturates, its mean-field back-reaction leaves the medium with a residual pressure proportional to $\lambda_0^2$ that suppresses the growth of the largest scales by a smooth factor and vanishes in the cold-matter limit $\lambda_0\to0$.

The symmetry-protected multiple Majorana zero modes (MZMs) can be manipulated under external fields and have emerged as a promising pathway toward realizing topological quantum computing. While the suitable materials hosting multiple MZMs are still scarce, we propose a feasible candidate platform named superconducting topological crystalline metals (STCMs) that simultaneously possess symmetry-protected topological bands and intrinsic superconductivity. Model analyses demonstrate that the interplay among s-wave superconductivity, mirror symmetry-protected multiple surface Dirac cones, and the introduced spin splitting leads to high BdG Chern numbers of $\mathcal{N} = \pm C_M$, where $C_M$ is mirror Chern number of the STCM. First-principles calculations identify the experimentally synthesized superconductor ZrRuAs as a promising candidate with $C_M=2$, hosting two symmetry-protected surface Dirac cones. When integrated into a heterostructure with the ferromagnetic insulator (FMI) such as GdI$_{2}$, a topological superconducting phase with $\mathcal{N} = -2$ can be realized, giving rise to two branches of MZMs. This new scheme offers advantages of structural simplicity and tunability, making the FMI/STCM heterostructure an ideal platform for investigating multipole MZMs and novel topological qubit.

Generative models now propose millions of "stable" crystal structures, and their own referees have shown that stability is not discovery; no public benchmark asks whether a candidate has the physics to do a job. For superconductors the job is twofold: to pair, with a definite gap symmetry, and to become wire. We present a physics judge that answers both from a structure alone (DFT+U, a gated Wannier model, the full rank-4 RPA susceptibility on a $24^3$ mesh, the linearized gap equation, an irreducible-representation classifier, a manufacturability funnel) and measure what it says about what generators propose. With answer keys pre-registered before computing, the judge was calibrated on six known superconductors (Nb, Nb$_3$Sn, MgB$_2$, BaFe$_2$As$_2$, La$_{2-x}$Sr$_x$CuO$_4$, YBa$_2$Cu$_3$O$_7$), recovering the expected class in all six after two dated corrections. On the ruthenium analogue of the iron pnictide, with two runs and their criterion pre-registered the day before, it returns a null verdict at the same physical interaction where iron gives s$\pm$ ($\lambda_1 \le 0.0007$ versus 0.096; critical U 4.17 versus 0.97 eV); the pre-registered equal-alpha run fails the letter of the criterion, and we declare the resolution in favour of absolute U as post-hoc. The funnel reproduces the industrial map with thresholds fixed before running. Three generation audits follow: a descriptor sweep over 150 Materials Project metals re-finds the canon; 1,248 MatterGen structures yield 0 candidates that are new, stable and carry a pairing motif; mechanism filters over 47,893 compounds, validated by a blind hold-out, re-derive the community's analogies: geometry plus d-count is necessary but not sufficient. Generation re-finds what is known; judgment is the bottleneck. We propose a public benchmark over the eleven lists of AI-proposed superconductor candidates, none of which classifies gap symmetry.

We present an extensive molecular dynamics (MD) study of the dynamical properties of a binary hard-sphere fluid over a wide range of packing fractions, $\phi \approx 0.357-0.582$. The self-diffusivity, $D$, and shear viscosity, $\eta$, are computed using an efficient implementation of the Einstein–Helfand method. The finite-size effects in $D$ scale as $1/N^\alpha$, with $\alpha$ increasing from approximately $1/3$ to $3/4$ with increasing $\phi$, whereas those in $\eta$ are negligible except for $\phi \gtrsim 0.554$, where they scale as $1/N$. The data are then extrapolated to the thermodynamic limit to obtain $D_{\infty}$ and $\eta_{\infty}$. Both coefficients show a super-Arrhenius dependence on $\phi$ for dense states, accompanied by a breakdown of the Stokes–Einstein relation. Although both $D_{\infty}(\phi)$ and $\eta_{\infty}(\phi)$ data are well described by an exponential form, we demonstrate that these fits do not provide reliable estimates of the critical packing fraction, $\phi_0$, owing to the substantial extrapolation required beyond the accessible equilibrium range. We find the commonly assumed proportionality between $\eta$ and the structural relaxation time, $\tau_\alpha$ , to not hold for this system. For $\phi\gtrsim 0.570$, the van Hove self-correlation function $G_s(r, \tau)$ exhibits a spatial exponential decay at intermediate times, $\tau$, signaling dynamic heterogeneity. The characteristic decay length scales as $\lambda \sim \tau^\nu$, with $\nu \approx 1/3$, in contrast to the conventional square-root scaling. We also investigate temporal heterogeneity through the four-point dynamic susceptibility, $\chi_4(\tau)$, and its peak time, $\tau_4$. These findings provide rigorous benchmark MD data for computational studies of glassy dynamics and establish a reference for testing theoretical models in dense disordered systems.

Deciphering the microscopic details of crystal nucleation remains a key open problem in chemical physics. For aqueous sodium chloride (NaCl), the extent to which nucleation involves amorphous ion aggregation, and the supersaturation regime in which two-step-like behavior emerges, remains actively debated. In this work, we examine NaCl nucleation at 12, 13, and 14 mol/kg ($S = 3.2, 3.5, 3.8$) using unbiased path sampling with $\infty$RETIS. Through a combination of reaction coordinate analysis, joint and conditional probability distributions, diffusion tensor analysis, and conditional free energy landscapes, we identify nucleation pathways without a priori mechanistic assumptions. While all concentrations are governed by the same reaction coordinate, indicating that nucleus growth and structural ordering are central to crossing the barrier, the nature of reactive trajectories changes with supersaturation. At lower concentrations, nucleation mainly occurs via tightly coupled increases in cluster size and ordering, compatible with a one-step-like mechanism. As concentration increases, amorphous aggregation becomes increasingly decoupled from crystallization, and pathways involving substantial amorphous growth prior to crystallization become progressively more probable. Importantly, these pathways coexist within a single broad reaction channel rather than proceeding through distinct metastable intermediate states. Together, these results reconcile earlier, contradictory reports on NaCl nucleation mechanisms and support a view of nucleation as an ensemble of competing reactive pathways whose relative probabilities vary continuously with supersaturation. More broadly, our findings illustrate that substantial mechanistic diversity can emerge within a classical nucleation framework, without requiring distinct non-classical descriptions.

We calculate the intrinsic contribution to the (valley) thermal Hall conductivity of phonons in (Semenoff-gapped) graphene in the quantum Hall regime where bulk electron thermal transport is suppressed. The (valley) thermal Hall transport of phonons considered here originates from a phonon (valley) Hall viscosity induced by electron (valley) Hall conductivity and viscosity via geometric electron-phonon coupling. The so generated phonon (valley) Hall viscosity is identified with the emergent (valley) Hall viscosity recently introduced in Phys. Lett. A 595, 132096 (2026). While our calculations refer to graphene, they may very well be generalized to other Dirac materials like group-VI transition metal dichalcogenides. We discuss the prospect of measuring the phonon thermal Hall conductivity in graphene-based heterostructures and estimate the corresponding valley response induced by electrons in the inversion symmetry broken phase.

We extend the KTHNY theory of defect-mediated melting in two dimensions to the case of active solids exhibiting both non-reciprocal (odd) elasticity and Cosserat (micropolar) coupling. For perturbatively small values of non-reciprocity, melting still proceeds via defect unbinding, but the melting temperature shifts due to activity. However, at a threshold value of non-reciprocity, we discover a qualitatively distinct mechanism for 2D melting, which we call topological instability. This melting occurs through the proliferation of defect pairs at any temperature. We use a combination of field theory and simulations to characterize this zero-temperature transition in terms of the defect-pair fugacity. Surprisingly, for higher activity values, we find reentrant crystallization, where the quasi-long-range order survives even at temperatures for which the equilibrium crystal would melt. Although active solids present one realization of this topological instability, we envision core-energy-driven defect proliferation as a generic and unexplored route for two-dimensional melting.

In classical anharmonic lattices, the resonance structure driving nonlinear mode mixing is reshaped by band gaps. However, it remains unclear whether a spectral gap hinders or promotes long-time thermalization. Here we study a dimerized Fermi-Pasta-Ulam-Tsingou chain - a classical SSH model analogue with alternating spring constants - and quantify how the acoustic-optical gap controls relaxation under alpha-type (cubic) nonlinearity. Tracking modal energies and spectral entropy via long-time symplectic simulations, we find a sharp isolation threshold when the dimerization strength reaches half its maximum value, set by the onset of the first umklapp process that allows two zone-boundary acoustic phonons to fuse into a zone-center optical phonon; below this threshold, three-wave acoustic-acoustic-optical scattering activates the optical branch on timescales of order 1e4 oscillation periods, while above it the bands remain dynamically isolated. We further show that boundary conditions reshape this picture, producing long-lived sticky states for specific mode excitations. These results establish the phononic gap as a tunable, momentum-selective filter for nonlinear energy transport, suggesting a general route to controlling thermalization in dimerized or topologically gapped nonlinear lattices.

Light-driven control of material symmetry enables the engineering of phenomena forbidden in equilibrium. Although electromagnetic fields have been used to break time-reversal symmetry, its dynamic control on ultrafast timescales in nonmagnetic insulating oxides remains virtually unexplored. Here, we demonstrate simultaneous magnetic symmetry lowering and timereversal-symmetry breaking in cubic SrTiO3 driven by an off-resonant, elliptically polarized THz pulse. Second harmonic generation (SHG) polarimetry reveals emergent SHG circular dichroism inconsistent with third-order nonlinear processes under cubic m3m symmetry. The SHG polar patterns exhibit mirror-symmetry breaking, indicating a transient reduction to tetragonal 4/mm'm' magnetic symmetry. Furthermore, the SHG response scales linearly with the angular momentum of THz pulse, providing direct evidence for THz-field-induced timereversal-symmetry breaking. These results establish a direct pathway for ultrafast symmetry control in non-magnetic oxides, enabling dynamic manipulation of emergent phases on ultrafast timescales.

We establish an exact equivalence between the fluctuations of integrated currents and the temporal statistics of current record events in continuous-time Markov jump processes. Specifically, we show that, under minimal assumptions, the Fano factor of an integrated current coincides exactly with the squared coefficient of variation of the inter-record waiting times. This result is obtained by showing that inter-record times induce a renewal structure, since each record event resets the system to a fixed state, and that their generating function can be expressed exactly in terms of a combinatorial organization governed by Narayana numbers. The equivalence extends previous results obtained for unicyclic networks to arbitrary finite-state graphs and provides a unified representation of current fluctuations in terms of record-time observables. The results are derived within a purely probabilistic framework and clarify the structural origin of current precision in terms of first-passage-like event statistics.

We systematically investigated the phase stability and pressure dependence of the elastic properties of four GeO2 polymorphs: rutile-, CaCl2-, alpha-PbO2-, and pyrite-type phases using theoretical calculations based on density functional theory. The elastic constants were calculated at 5 GPa intervals within the respective stability ranges of the four phases, as determined from static enthalpy calculations. We further employed a classical strain-coupled Landau free-energy expansion to describe the pressure evolution of the elastic response associated with the rutile- to CaCl2-type transition and to elucidate the origin of the elastic softening near the transition. The rutile- to CaCl2-type phase transition is consistent with a Landau-type second-order transition, with a critical pressure of 14.6 GPa obtained from the strain-based analysis. As the transition pressure approaches, elastic softening develops in the rutile-type phase, resulting in anomalous pressure dependence of the bulk and shear modulus. The calculated elastic-wave anisotropy increases markedly near the transition, primarily due to the rapid reduction in shear-wave velocity, reaching a maximum of approximately 122% at 22.5 GPa. Following the transition, the anisotropy decreases sharply in the CaCl2-type phase and exhibits a discontinuity at the CaCl2-type/alpha-PbO2 -type phase boundary. The higher-pressure alpha-PbO2- and pyrite-type phases exhibit comparatively weak pressure dependence of anisotropy, with a small discontinuity at their respective phase transition boundaries. The pyrite-type phase has the lowest anisotropy, reaching only approximately 4-5% at high pressure, consistent with the high-symmetry cubic structure and nearly isotropic elastic-wave propagation.

Prethermal states–long-lived quasi-equilibrium configurations–occur in a wide range of physical systems that exhibit fast dephasing or reconfiguration followed by slow relaxation towards thermal equilibrium. We experimentally studied the 1D interface between immiscible 2D Bose-Einstein condensates (BECs); following a quench, the interfacial capillary waves (ripplons) quickly relaxed into a long-lived prethermal state characterized by a persistent non-equipartition of energy, evoking the classic Fermi-Pasta-Ulam-Tsingou problem. We directly measured the interface's height profile as it evolved in time, identified the contribution of individual ripplon modes, and find that, though their individual amplitudes are thermally distributed, they are not in thermal equilibrium–high-momentum modes rapidly equilibrated with the bulk phonon modes of the 2D BEC, while lower momentum modes remained at elevated temperatures, forming a long-lived prethermal configuration for the whole system. We attribute this to kinematic isolation: the absence of energy- and momentum-conserving relaxation processes in our system at ultracold temperature.

Ultracold atomic quantum systems offer an unprecedentedly powerful platform for exploring interacting symmetry-protected topological phases. Here, we show that their characteristic control over temperature provides a resource for engineering effective topological regimes with no zero-temperature counterpart. Employing finite-temperature matrix-product-state calculations, we investigate experimentally accessible Hamiltonians - the interacting bosonic Su-Schrieffer-Heeger and spin-1 XXZ chains - that host a topological phase at zero temperature, as well as a fermionic dipolar ladder model whose ground state exhibits no topological order. By tracking complementary topological markers, we identify an intriguing mechanism rooted in the structure of the zero-temperature phase diagrams: in finite-size systems, excitation gaps with different magnitudes define an intermediate-temperature window where the correlations associated with the lower gap are suppressed, while those protected by the larger gap persist. This enables the emergence of effective finite-temperature regimes exhibiting topological features that are either absent or qualitatively different from those at zero temperature. Our results establish a novel route toward exploring effective topological phases in ultracold atomic quantum systems.

Lutetium hydrides (LuH$_x$, $1.75 \leq x \leq 3$) form a diverse series of phases, several of which superconduct under pressure. Characterizing their electronic properties has remained challenging owing to a high propensity for hydrogen defect formation, and recent angle-resolved photoemission (ARPES) measurements reveal puzzling flat-band regions that position these materials as candidates where superconductivity and flat-band physics may intersect. Here, by combining density functional theory, dynamical mean-field theory, and the constrained random-phase approximation, we uncover the microscopic origin and correlation nature of these flat bands. Across all compositions, the screened on-site Coulomb interaction is larger for H-s states than for Lu-$d$ states due to compact hydrogen orbitals. Nevertheless, these systems remain weakly correlated metals: the nearly filled H-$s$ shell admits little charge fluctuation, so its large interaction acts as a static level shift rather than a source of correlation. Although hydrogen primarily occupies tetrahedral sites at $x=2$, we discover that anti-site defects–where hydrogens occupy slightly unfavorable octahedral sites–generate both the ARPES flat-band features and the low-energy optical absorption peak, attesting to the usual defective nature of such materials in experimental samples. We further find that correlation strength is governed primarily by hydrogen orbital filling at these sites rather than the interaction magnitude itself. Consequently, we identify hydrogen orbital filling as the fundamental organizing principle dictating correlation and low-energy flat-band physics in lutetium hydrides.

Fractional quantum anomalous Hall effect (FQAHE) has been discovered in twisted MoTe$_2$ and rhombohedral graphene/hBN moiré superlattices. Such van der Waals heterostructures feature a tuning knob of gate displacement field $D$, which is absent from the conventional fractional quantum Hall systems in two-dimensional electron gases. $D$ plays a critical role in engineering FQAHE and other emergent quantum states and provides an exciting new opportunity to explore their quantum phase transitions. However, the microscopic details of such transitions and temperature-dependent transport have remained mostly elusive. Here we report systematic resistance measurements in rhombohedral pentalayer graphene/hBN moiré superlattices. We found that the displacement field-driven phase transitions between Composite Fermi liquid, Fermi liquid, Fractional Chern insulators, and insulating states are described by semi-circle relations of the longitudinal and transverse resistivities (or conductivities), largely unexplored in the fractional quantum Hall systems. This agrees with a spatially separated two-phase picture for the phase transitions and further indicates a new insulator phase–fractional quantized anomalous Hall insulator. By comparing the temperature-dependence of longitudinal resistance with the thermal activation model, we estimated the transport gap sizes in three fractional Chern insulator states. Our work shed light on the quantum and temperature evolutions of fractional Chern insulator states–providing necessary background for anyon-braiding and gate-defined junctions in rhombohedral graphene.

Dense granular flows are a common occurrence throughout nature and industry, but still exhibit phenomena that are not fully understood. One of these phenomena is the segregation of particles that constitute a dense granular flow, where particles separate due to differences in properties such as size and density. This work approaches segregation from a new perspective by developing a force model for a single particle based on the observation that there are two opposing drag forces acting on the particle. Validation of the model in mono-disperse flows reveals a family of velocity profiles, including a Bagnold profile. Further validation is done by comparing with known particle scaling laws in literature. The force model shows that the mechanism of segregation is always present in dense granular flows and that mono-disperse flows are a unique case where it is not distinctly visible. The insights in this paper prove a fundamental new way of thinking about dense granular flows and its individual particles, opening the field for new research directions.

Collective order is notoriously difficult to stabilize in one dimension, where strong fluctuations suppress symmetry-breaking states. Here we report the emergence of an electronic bond-order wave (BOW) in the quasi-one-dimensional (1D) material Ba9Rh8O24, in which structural bonds become active electronic degrees of freedom that overcome 1D fluctuations to establish long-range order. Single-crystal X-ray diffraction uncovers a striking inversion of inequivalent Rh-Rh bonds across a transition TA = 180 K, where short and long bonds interchange their identities rather than undergoing conventional Peierls dimerization. This bond inversion coincides with a heat-capacity anomaly and a profound reorganization of the dielectric response with strong suppression of dielectric loss upon cooling. The BOW exhibits strongly nonlinear, frequency-dependent I-V characteristics, clockwise hysteresis, and nonvolatile memristive switching. These findings uncover an unprecedented transformation from a dynamic bond liquid to a rigid yet electrically reconfigurable BOW, establishing bond-centered electronic order as a new organizing principle for 1D quantum matter.

The Charge Density Wave (CDW) state is a perfect example of a combined structural and electronic state, both characterized by a periodic lattice distortion and an electronic modulation of condensed electrons, resulting from electron-phonon coupling. They are thus prone to be tuned by lattice strain. NbSe3 is a prototypical example of CDW states, with a chain-like structure displaying two CDWs at 145K and 59K, with wavevectors along and inclined with respect to the chain axis b. Here, we report on the evolution of the lattice structure and CDW properties in the quasi-one-dimensional charge-density-wave system NbSe3 under tensile stresses applied along and perpendicular to the chains axis b by a combination of X-ray diffraction and transport measurements. We find that the lattice structure show exotic Poissons coefficients and strongly anisotropic Youngs moduli while the evolution of the electrical resistance demonstrates shifts of both charge-density-wave critical temperatures that are strongly correlated with the lattice parameters. The two CDW transitions display different behaviours under applied stresses, and suggest that a modification of the band curvature leads to the observed transport signatures.