We report the temperature-dependent synchrotron based x-ray diffraction analysis of NASICON type ${\mathrm{Na}}_3\mathrm{FeCr}{\left({\mathrm{PO}}_4\right)}_3$ sample, which undergoes a symmetry-lowering structural transition from a monoclinic ($C2/c$) phase with long-range Na-vacancy order to a rhombohedral ($R\overline{3}c$) phase with statistical disordered Na ions. The [FeCr(${\mathrm{PO}}_4{)}_3$] polyanionic framework remains essentially unchanged, confirming that the transition is governed by redistribution of the Na sublattice rather than by reconstruction of the host framework. The structural evolution is accompanied by a discontinuous increase in the $c$ axis and the unit-cell volume, reflecting the progressive depopulation of the Na(1) sites and transfer of Na ions toward the Na(2) sublattice. The temperature dependence of superstructure intensity is found to deviate from mean-field critical behavior, instead, the experimental evolution is accurately captured by a sigmoidal phase-fraction model. The calorimetric measurements show that the enthalpy change for the first transition around 350 K is significantly larger than that of the anomaly around 445 K, indicating the dominant configurational rearrangement of Na ions occurs within the lower-temperature interval. Overall, the diffraction and calorimetric results demonstrate that Na ordering proceeds through an order-disorder transition involving intermediate Na configurations and a finite coexisting regime. The quantitative correlation between Na-vacancy ordering, lattice strain, and symmetry lowering reveals the central role of configurational interactions within the Na conduction channels in governing the phase stability of NASICON-type materials.

For the two-dimensional Lieb lattice, while intrinsic spin-orbit coupling (SOC) is responsible for opening the gap that exhibits the quantum spin Hall effect, topological phase transitions are driven by a real next-nearest-neighbor (NNN) hopping. Using the transfer-matrix method on a quasi-one-dimensional stripe with transverse periodic boundaries, we study the flat-band localization mechanism in the presence of complex NNN hoppings. We demonstrate that the geometric localization in flat bands can be alleviated by the extended nature of topological bulk states when SOC opens a topological gap. Furthermore, correlated disorders are shown to induce inverse Anderson localization with the topological edge states persisting under strong disorder, a robustness confirmed by Chern number calculations, which identifies the root cause of this phenomenon. These findings establish a unified platform for investigating topological phase transitions, flat bands, and disorder effects.

With the extended Su-Schrieffer-Heeger model and Green's function method, we theoretically demonstrate a significant spin-filtering effect in organic antiferromagnetic (AFM) junctions without any ferromagnetic elements or chiral structures. The spin filtering is caused by the large spin splitting of the destructive quantum interference (DQI) features, which results from the coexistence of the DQI and molecular AFM state. An analytical analysis based on Green's function indicates that the nondegenerate AFM wave functions of frontier orbitals is the source of the spin-resolved DQI. The electron-electron interaction is found crucial to achieve the AFM phase and thus the large spin polarization around the Fermi energy. The results are further confirmed by first-principles calculations. The robustness of the proposed mechanism under finite bias voltages and the generality of such effect in other organic AFM molecules are further examined. This work provides a new route to achieve large spin polarization in AFM junctions without ferromagnetic elements, and opens new avenues for organic AFM molecules as well as quantum interference effect in molecular spintronics.

${\mathrm{Li}}_2{\mathrm{AuH}}_6$ and ${\mathrm{Li}}_2{\mathrm{AgH}}_6$ have been proposed as promising candidates for high-temperature superconductors under ambient pressure. While previous studies confirm the dynamic stability of these two thermodynamically unstable systems, their kinetic stability against quantum and thermal fluctuations remains to be verified. In this work, we use path integral molecular dynamics simulations to examine the kinetic stability of ${\mathrm{Li}}_2{\mathrm{AuH}}_6$ and ${\mathrm{Li}}_2{\mathrm{AgH}}_6$ under ambient pressure. We find both compounds are kinetically unstable. ${\mathrm{Li}}_2{\mathrm{AgH}}_6$ undergoes lattice collapse, whereas ${\mathrm{Li}}_2{\mathrm{AuH}}_6$ retains a stable fluorite-type Li-Au sublattice, but hydrogen atoms partially dimerize into molecules and diffuse within the host lattice. Using the stochastic path-integral approach, which is a nonperturbative approach applicable to systems with diffusive atoms, we investigate the superconductivity of ${\mathrm{Li}}_2{\mathrm{AuH}}_6$ in this state. We predict a superconducting transition temperature of 22 K, well below earlier predictions, due to the low density of states at the Fermi level caused by the collapse of hydrogen sublattice and hydrogen dimerization.

Ferroelectric topological textures have attracted growing interest as nanoscale polarization states with rich structural and functional behavior. Here, using phase-field simulations, we study the controlled formation and stability of polar bubbles in square lead zirconate titanate nanodots. We show that zero-field-stable polar bubbles can be generated through an electric-field poling–depoling process: an out-of-plane electric field first drives the nanodot into a nearly single-domain state, and subsequent field removal allows spontaneous relaxation into a toroidal bubble configuration. We further examine how geometry, epitaxial misfit strain, temperature, and electrostatic screening regulate bubble morphology and stability. The results show that intermediate geometries favor single-ring polar bubbles, very small lateral sizes stabilize stripelike domains, and larger, thinner nanodots promote multiring target-skyrmion states. Moderate screening and weak compressive strain further stabilize fully enclosed polar bubbles over a broad temperature range. Electric-field cycling reveals reversible switching through contraction, collapse, and reformation of the ringlike domain wall. These results provide a unified physical picture of polar-bubble formation and tunability in confined ferroelectric nanostructures, offering insight into the mechanisms governing nanoscale ferroelectric textures.

We report a combined experimental and computational study of the polar nature of twin walls (TWs) in calcite. Second-harmonic generation (SHG) imaging reveals that $\left\{01\overline{1}8\right\}$ TWs exhibit clear second-harmonic  activity, whereas $\left\{10\overline{1}4\right\}$ TWs show no detectable response under any polarization configuration. Polarization-resolved SHG measurements demonstrate that the SHG signals at $\left\{01\overline{1}8\right\}$ TWs are consistent with a symmetry reduction from the bulk centrosymmetric structure ($R\overline{3}m$) to point group $m$. Molecular dynamics simulations clarify the microscopic origin of this polarity: At $\left\{01\overline{1}8\right\}$ TWs, charge-center displacements are confined to two atomic layers, giving rise to localized electric polarization, while at $\left\{10\overline{1}4\right\}$ TWs, alternating displacements in adjacent layers effectively cancel the net electric polarization. The simulations further reveal strong coupling between interfacial electric polarization and shear stress, as well as suppression of electric polarization with increasing temperature. These findings establish the atomic-scale mechanism of polarity at calcite TWs and provide a framework for understanding polar domain boundaries in centrosymmetric crystals.

Kinetic constraints in quantum many-body systems strongly restrict the accessible Hilbert space, giving rise to highly nontrivial dynamical behavior. In recent years, such systems have attracted growing interest as they provide insight into mechanisms of thermalization and into regimes where thermalization fails. In this work, we study a family of rule-based kinetically constrained models, including the celebrated Quantum Game of Life, from the perspective of quantum complexity, with a focus on entanglement, nonstabilizerness, and quantum chaos. Using spectral diagnostics such as level statistics and spectral form factors, we show that these models exhibit robust chaotic behavior while simultaneously supporting both strong and weak Hilbert-space fragmentation and quantum many-body scar states. Our results reveal that the nature of Hilbert-space fragmentation can be tuned qualitatively from strong to weak fragmentation and ultimately to its absence, within a single family of models through simple variations of the underlying kinetic rules. To further elucidate the structure of these fragmented subspaces, we characterize them through their ability to generate quantum resources. In particular, we show that resource-generation capacity does not necessarily correlate with the dimensionality of a fragmented sector, and that entanglement structure and the ability to generate nonstabilizerness provide effective diagnostics for distinguishing dynamically disconnected sectors, including those supporting nonthermal scarred dynamics. Our work thus places kinetically constrained models within a broader and more general framework, not limited to Rydberg-blockade-based constraints only, and demonstrates that simple variations in underlying rules can lead to qualitatively distinct static and dynamical regimes including chaotic, fragmented, and scarred phases that remain largely unexplored in previous works that can be instrumental for both the fundamental understanding and quantum technological applications of these models.

By coupling Bardeen-Cooper-Schrieffer (BCS) theory with isolated bands to an external gravitomagnetic vector potential via a gravitomagnetic Peierls substitution, we identify a quantum-geometric contribution to the electronic contribution of the thermal conductivity. This contribution is governed by the quantum metric in the parameter space spanned by the components of the external gravitomagnetic vector potential which corresponds to a weighted quantum metric in momentum space. In the flat-band limit, we establish an upper and lower Wiedemann-Franz-type bound for the ratio of thermal Meissner stiffness and electric Meissner stiffness (superfluid weight), whose prefactors are provided by the extrema of the squared energy offsets of the outer single-particle bands of the system. Similarly to the superfluid weight, this also leads to a lower bound of the thermal Meissner stiffness in terms of the Chern number. Our results apply to both superconductors and other fermionic superfluids.

We investigate the effect of dilute Ir substitution on the magnetism of the trimer-based ruthenate ${\mathrm{Ba}}_4{\mathrm{Ru}}_3{\mathrm{O}}_{10}$ using neutron diffraction, magnetic susceptibility measurements, first-principles calculations, and atomistic simulations. Neutron diffraction shows that Ir doping preserves the zigzag antiferromagnetic structure and the ordered-moment magnitude of the parent compound, in which the moments reside exclusively on the two outer Ru(2) sites of each ${\mathrm{Ru}}_3{\mathrm{O}}_{12}$ trimer, while the central Ru(1) site remains nonmagnetic. The Néel temperature is reduced from $\sim 105$ to 84.0(1) K upon 8% Ir substitution, while magnetic susceptibility reveals a pronounced low-temperature Curie-like upturn, indicating the coexistence of paramagnetic spins with long-range antiferromagnetic order. Density-functional calculations show that Ir preferentially occupies the central Ru(1) site, which disrupts the exchange pathways of the affected ${\mathrm{Ru}}_3{\mathrm{O}}_{12}$ trimer state. Atomistic simulations incorporating this paramagnetic dilution reproduce the suppressed ordering temperature and the coexistence of ordered and paramagnetic components.

Kagome magnets provide fertile platforms for field-tunable magnetic phases, electronic correlations, and quantum phenomena. However, the in-plane anisotropy within the kagome layers remains largely unexplored. Here we report the synthesis of ${\mathrm{Gd}}_3{\mathrm{TiBi}}_5$ single crystals featuring distorted Gd kagome layers, which exhibit an antiferromagnetic transition at $T_{\mathrm{N}}\approx 19\mathrm{K}$ and a pronounced in-plane anisotropic magnetization. The magnetic phase diagrams display successive field-driven magnetic phases separated by well-defined, anisotropic phase boundaries, indicating complex reorientation processes of ${\mathrm{Gd}}^{3+}$ moments under external magnetic fields. Notably, the in-plane angle-dependent magnetoresistance (ADMR) measurements uncover a snowflake-like ADMR pattern at low temperatures and under high magnetic fields, characterized by a pronounced sixfold symmetry with narrowed central spikes and additional shoulder-like modulations along each lobe. The sixfold ADMR is primarily attributed to the in-plane anisotropic magnetic transitions, highlighting the coupling between localized $\mathrm{Gd}\text{−}4f$ moments and itinerant electrons. DFT calculations further suggest that rotating the magnetic moment direction can drive a van Hove singularity across the Fermi level, potentially inducing a spin-orientation-dependent Fermi-surface reconstruction. These results establish ${\mathrm{Gd}}_3{\mathrm{TiBi}}_5$ as a promising platform for studying the interplay between frustrated magnetism and electrical transport and provide a useful framework for understanding magnetism-driven anisotropic transport.

Employing angle-resolved photoemission spectroscopy (ARPES), we have investigated the electronic structures of Sb-substituted ${\mathrm{CeTe}}_2, {\mathrm{CeTe}}_{2-x}{\mathrm{Sb}}_x$ ($0\le x\le 0.5$), which exhibit charge density wave (CDW) transitions and enhanced thermoelectric (TE) properties and are also predicted to be topological material candidates. Two flat Ce $4f$ states are observed, one at approximately $-3.5\mathrm{eV}$ and the other at approximately $-0.8\mathrm{eV}$, which represent the $4f^1\to 4f^0$ transition and the Kondo-like $4f^1{\overline{L}}^0\to 4f^1{\overline{L}}^1$ transition (where $\overline{L}$ is a ligand hole) of trivalent ${\mathrm{Ce}}^{3+}$ ions, respectively. Two diamond-shaped inner and outer Fermi surfaces (FSs) are observed, which arise from the holelike band centered at $\mathrm{\Gamma }$ and from the folding of the two-dimensional Brillouin zone (BZ) into the three-dimensional (3D) BZ, respectively. The measured outer FSs demonstrate the non-negligible effect of the 3D electronic structures of ${\mathrm{CeTe}}_{2-x}{\mathrm{Sb}}_x$. The CDW-induced zigzag features are observed in the FS of $x=0$, but are not observed in the FSs of $x>0$, indicating the rapid suppression of the CDW state by the Sb substitution. This finding suggests that the increased resistivity at $x>0$, despite the weakened CDW formation, is possibly due to the disorder-induced localization by the Sb substitution, leading to the optimal TE properties at a specific $x$. The measured band structures of ${\mathrm{CeTe}}_{2-x}{\mathrm{Sb}}_x$ via ARPES exhibit very similar features for different $x$ values, except for the shift of the whole bands toward the Fermi level ($E_{\text{F}}$) with increasing $x$. This reflects the hole doping introduced by the Sb substitution, which is in good agreement with the calculated band structures. In the ARPES data of $x>0$, crossing bands are observed near the $X$ point at approximately $-1\mathrm{eV}$, which closely resemble Dirac points, suggesting the existence of topological electronic structures of ${\mathrm{CeTe}}_{2-x}{\mathrm{Sb}}_x$. Linear dichroism ARPES measurements on ${\mathrm{CeTe}}_{1.75}{\mathrm{Sb}}_{0.25}$ show that the $E_{\text{F}}$-crossing Te/Sb $p$ states along $X\text{−}\mathrm{\Gamma }\text{−}X$ and $M\text{−}\mathrm{\Gamma }\text{−}M$ have both in-plane and out-of-plane character, while those along $M\text{−}X\text{−}M$ have mainly in-plane character.

Dispersively coupled distant qubits in a shared cavity can become entangled through virtual photon exchange with energy-conserving phase evolution of their quantum states. This interaction can potentially be accelerated by operating on resonance, allowing for the exchange of real photons. In this theoretical study, we examine photon-mediated entanglement between two distant spins of electrons confined in double quantum dots formed in a Si/SiGe heterostructure. We calculate the dynamics of the combined system comprised of both spin qubits and the cavity, assuming that both spin qubits can be tuned into and out of resonance with the host cavity. We demonstrate that the exchange of real photons between the two spin qubits can result in rapid entanglement that is robust against decoherence. These results pave the way for the development of quantum gates on resonantly coupled distant semiconductor spin qubits.

Altermagnetism provides a promising platform for valleytronics applications due to its symmetry-protected spin-valley locking. While uniaxial strain and in-plane magnetization have recently emerged as novel routes to induce valley polarization in altermagnets, a unified theoretical framework elucidating their microscopic mechanisms remains absent. Here, we use a tight-binding (TB) model to show that both uniaxial strain and in-plane magnetization can induce valley polarization in two-dimensional (2D) tetragonal altermagnets by breaking the $C_{4z}\mathcal{T}$ symmetry, although driven by distinct mechanisms. Specifically, uniaxial strain tunes valley polarization by modulating anisotropic hopping, yielding a monotonic dependence whose sign can be reversed by switching the strain axis ($x/y$) or type (compressive/tensile). In contrast, in-plane magnetization generates valley polarization via weak ferromagnetism, exhibiting a characteristic $cos2\varphi$ dependence determined by the spin direction. Crucially, these model predictions are confirmed by first-principles calculations on a $d$-wave altermagnet monolayer ${\mathrm{Mo}}_2{\mathrm{Te}}_2\mathrm{O}$, demonstrating tunable valley polarization. Our findings establish a unified theoretical framework for the control of valley polarization in 2D tetragonal altermagnets, providing a foundation for the development of valleytronics.

Metamaterials provide a versatile platform for realizing topological phases and exploring non-Hermitian physics. However, the design of metamaterials exhibiting such rich physics is challenging because conventional design approaches require constant iterative optimization, which unfortunately is both time-intensive and computationally expensive. Here, a noniterative reverse design strategy based on tight-binding models is proposed. Our design starts with topolectrical circuits; by exploring the equivalence of scattering properties between circuits and waveguides, we demonstrate that a lumped-element circuit can be directly translated to its metamaterial counterpart. As a proof of concept, we design electromagnetic metamaterials based on three representative models. For the Hermitian case, a honeycomb lattice that preserves time-reversal symmetry ($T$), and the Haldane model with $T$-breaking nonreciprocal hoppings are implemented; whereas for the non-Hermitian case, a topological heterojunction exhibiting non-Hermitian skin effect is constructed. Given the widespread use of scattering parameters, the proposed strategy can be generalized to the design of metamaterials in systems beyond electromagnetics. Our work reveals an efficient and straightforward approach for realizing topological phenomena in classical wave systems, offering a deterministic alternative for the design of topological devices.

The moiré pattern, which emerges due to a relative rotation between two monolayers of transition metal dichalcogenides, features a long lattice period for small twist angles. The resulting band-structure modulation acts as an effective potential for interlayer excitons, which can realize correlated many-body phenomena. Here, we aim for a material-realistic modeling of the interlayer exciton-exciton interaction, taking into account lattice reconstructions and an exciton-exciton potential that incorporates the highly anisotropic screening imposed by the two-dimensional bilayer and the dielectric background. We find strong modifications of the on-site interaction induced by the change of the moiré potential during lattice reconstructions, while for long-range interactions on the length scale of the moiré period, anisotropic dielectric screening leads to a crossover from a repulsive to an attractive interaction. The interaction potential and hopping amplitudes serve as parameters for a Bose-Hubbard model on the moiré lattice, which we use to explain the correlated behavior of interlayer excitons.

The observation of $\mathrm{high}\text{−}{T}_{\mathrm{c}}$ superconductivity in bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under high pressure provides a new venue for exploring novel unconventional superconductors and elucidating the mechanism of $\mathrm{high}\text{−}{T}_{\mathrm{c}}$ superconductivity. Subsequently, numerous chemical substitution studies have been reported, aiming to stabilize superconductivity at ambient pressure or significantly reduce the pressure threshold required for its occurrence. Here, we report the comprehensive study of sodium (Na) doping in the Ruddlesden-Popper nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_{7+\delta }$, where $\mathrm{N}{\mathrm{a}}^{+}$ substitutes for $\mathrm{L}{\mathrm{a}}^{3+}$ at the A-site with varying doping concentrations $\left(x\right)$. The structural, thermal, magnetic, and electronic transport properties of as-synthesized polycrystalline samples were systematically investigated. X-ray diffraction analysis reveals that the dominant structure has changed from the 327 Amam phase to the 4310 Bmab phase when $x\ge 0.075$, which is further corroborated by thermogravimetric analysis measurements. Substitution of $\mathrm{L}{\mathrm{a}}^{3+}$ with $\mathrm{N}{\mathrm{a}}^{+}$ within the 327 phase gives rise to a gradual expansion of the lattice. Meanwhile, resistivity measurements indicate that the resistivity anomaly associated with a density-wave-like (DW-like) transition is marginally suppressed and metallicity is significantly enhanced. Upon application of pressure, the DW-like transition can be further suppressed, whereas the low-T insulating behavior remains insensitive to pressure. These results offer critical insights into the roles of elemental substitution and charge carrier doping in steering the competing electronic phases in layered nickelates.

The nonlinear Hall effect has emerged as an essential field in condensed matter physics for its connection with the properties of quantum geometry and its potential application in electronic devices. However, when the nonlinear Hall current scales quadratically with a single driving electric field, it is difficult to regulate the direction of the Hall response by reversing the driving electric field. This limitation hinders the practical implementation of nonlinear Hall effect in logic memory applications. Here, we establish a symmetry-based framework for the nonvolatile control of the nonlinear Hall effect through ferroelectric switching in two-dimensional ferroelectric materials. We prove that ferroelectric switching reverses the effective spin-orbit field, thereby reversing the sign of the Berry curvature dipole and, consequently, the nonlinear Hall conductivity. Using symmetry analysis and tight-binding models, we identify 18 layer groups that allow a ferroelectric switchable nonlinear Hall effect driven by Berry curvature dipole. By first-principles calculations we demonstrate that the monolayer $\alpha \text{−}\mathrm{Bi}$ and ${\mathrm{NbOI}}_2$ are ideal platforms to verify our proposed switchable mechanism. Our results provide a generalized framework for the nonvolatile control of nonlinear Hall effect, paving the way for its potential application in logical storage through assisting in the detection of two-dimensional ferroelectric polarization states.