The temperature-dependent electric field gradient (EFG) tensor at a probe nucleus reflects the combined effects of local symmetry, bonding, and lattice dynamics. However, determining the primary atomic distortions responsible for this response can be difficult. Here, we combine electron-gamma (e-γ) time-differential perturbed angular correlation (TDPAC) measurements on ${}^{181}\mathrm{Ta}$ probes produced by the ${}^{181}\mathrm{Hf}\to {}^{181}\mathrm{Ta}$ decay at substitutional Ti sites in rutile ${\mathrm{TiO}}_2$ with symmetry-resolved local frozen-phonon density functional theory (LFP-DFT) calculations. Atomic displacements of the ${\mathrm{TiO}}_6$ octahedron are decomposed into site-symmetry-adapted local modes, and their contributions to the EFG are thermally weighted via Boltzmann averaging. We find that, in pristine rutile ${\mathrm{TiO}}_2$, the temperature evolution of the EFG shape is primarily governed by two orthogonal ${\mathrm{B}}_{1\mathrm{g}}$ equatorial-oxygen shear distortions. For Ta substituting the Ti site, the same shear sector remains active but preserves a finite in-plane anisotropy, resulting in a comparatively weak temperature dependence of the asymmetry parameter η. Measurements between 30 and 470 K, together with earlier high-temperature gamma-gamma $\left(\gamma \text{−}\gamma \right)$ data, show weak low-temperature curvature and high-temperature quasilinearity of the principal EFG component $V_{33}\left(\mathrm{T}\right)$, while η(T) remains comparatively robust. The calculations reproduce these qualitative trends and provide a microscopic, symmetry-based interpretation of the thermal evolution of hyperfine tensors in solids.

We propose a family of layered quantum spin-orbital models as a platform to study fractionalization, unconventional forms of symmetry-breaking order, and their possible coexistence. The models are built by stacking $N$ layers of a square-lattice system in which Kitaev-type interactions promote the formation of a ${\mathbb{Z}}_2$ quantum spin-orbital liquid and coupling the different layers via Ising spin interactions. Using a parton construction, we show how, at low energies, these Hamiltonians can be mapped to $N$-component Fermi-Hubbard models on a $\pi$-flux square lattice at half-filling. We also demonstrate that the models acquire an emergent $\mathrm{SU}\left(N\right)$ symmetry in the limit of equal all-to-all interlayer couplings and argue that, for $N>2$, the proximity to this limit offers the potential to realize an array of competing phases. To illustrate this point, we compute the zero-temperature phase diagram of the effective $N=3$ Hubbard model within mean-field theory and uncover rich phenomena, including intertwined orders and flavor-selective localization. Mapping back to the original degrees of freedom reveals that the ground states realize distinct forms of magnetic fragmentation, wherein the orbitals remain in a quantum liquid state whereas the spins can present conventional long-range order or nonlocal order characterized by a nontrivial string order parameters. We highlight possible extensions of our construction as well as its potential to provide concrete microscopic models for different fractionalized quantum critical points.

We propose an optical scheme to realize an exciton spin supersolid in an excitonic insulator formed in atomic double layers. By coupling exciton internal levels with three spatially modulated laser fields in an inverted-tripod configuration, an effective non-Abelian gauge potential is generated for the center-of-mass motion of excitons. This gauge field shifts the energy minima to finite in-plane momenta, driving the system into two distinct exciton condensate phases: a plane-wave condensate with uniform phase coherence, and more strikingly, an exciton spin-density wave. The latter phase exhibits a hallmark of spin supersolidity, simultaneously possessing superfluid coherence and periodic modulation of the spin density. Its excitation spectrum reveals two gapless Goldstone modes and a distinct periodic structure, originating from the spontaneous breaking of the $U\left(1\right)$ phase symmetry of the condensate and continuous spatial translational symmetry.

We develop a systematic framework for constructing all-bands-flat (ABF) lattice Hamiltonians that explicitly break time-reversal symmetry (TRS). By threading magnetic flux through disconnected polygonal plaquettes and applying local entangling unitary transformations, we map plaquettes onto families of ABF models in one, two, and three dimensions. This procedure preserves the flux configuration while converting semidetangled geometries into ABF lattices with nontrivial hopping structure. The resulting flat bands admit compact localized states (CLSs) whose support includes both the flux-threaded plaquettes and auxiliary sites introduced by the unitary transformations. In these TRS-broken constructions, the CLSs host localized circulatory currents whose magnitude depends on the applied flux. We further extend the framework to lattices with coexisting flat and dispersive bands, illustrating cases with both orthogonal and nonorthogonal CLSs. Our results provide a controlled route for generating dispersionless lattices supporting flux-induced local currents.

We derive explicit strong-field asymptotics for the normalized differential resistance in Hall field-induced resistance oscillations (HIRO) within the Vavilov-Aleiner-Glazman kinetic framework. For a single-harmonic density of states, the leading oscillation amplitude is set by the full backscattering rate $1/\tau \left(\pi \right)$. Extending the theory to a two-harmonic density of states, we show that the off-diagonal mixed kernel ${\gamma }_{12}$ admits an exact single-integral representation, from which the strong-field asymptotics follow directly. The resulting odd harmonics, notably $m=1$ and $m=3$, have coefficients determined by combinations of $1/\tau \left(0\right)$ and $1/\tau \left(\pi \right)$, while the leading $m=2$ amplitude remains unchanged. On exact-kernel mock data generated and fit within the same model, with ${\tau }_{\mathrm{tr}}$ and ${\tau }_{\mathrm{in}}$ held fixed, the resulting extraction protocol recovers ${\tau }_q, \tau \left(\pi \right)$, and—when the $m=1,3$ harmonics are resolved—$\tau \left(0\right)$ to subpercent accuracy, with $\tau \left(0\right)$ providing a consistency check on the disorder description.

Topological degeneracies (TD) and half vortices with nontrivial charges have been widely studied in various metastructures, which mainly relies on the symmetry breaking of structures. Here, by resorting to material anisotropy rather than geometric asymmetry, we designed a layered anisotropic dielectric system and found that rotating the optical axis (OA) of one layer not only breaks the symmetry of such layered system but also brings TD and circularly polarized states (C points) that are absent in single-layer anisotropic system. In detail, two bulk Fermi arcs with pairs of exceptional points can evolve into a pair of Dirac point, and the two Dirac points will eventually annihilate as the rotates along the polar direction. During this process, C points will merge and undergo the charge exchange with degenerate points. When rotating the OA in the direction of azimuth angle, a quadratic degeneracy can be split into a pair of Dirac points, or vice versa. Our work reveals the modulating effects of anisotropy on TD and singularities, paving the way for exploring more topological physics in naturally anisotropic materials without specific structural design.

Simultaneously enhancing the power factor and suppressing lattice thermal conductivity is the primary challenge in designing high-performance thermoelectric materials. In tetradymite topological insulators ${\mathrm{Bi}}_2{X}_{2}Y$, engineering Janus configurations offers a route to tune both electronic and phonon transport. First-principles calculations reveal that in Janus $\beta \text{−}{\mathrm{Bi}}_2{\mathrm{Se}}_2\mathrm{Te}$, Rashba splitting induced by broken inversion symmetry acts in concert with topological band inversion to enhance the effective band edge density of states, resulting in an improved power factor relative to its centrosymmetric $\alpha$-phase counterpart. Concurrently, the structural asymmetry of the Janus configuration enhances anharmonicity and expands the phonon scattering phase space, reducing the lattice thermal conductivity below that of the corresponding $\alpha$ phase across the full temperature range. This synergistic effect of both electronic and thermal transport enables Janus ${\mathrm{Bi}}_2{X}_{2}Y$ compounds to achieve theoretical figure of merit ($zT$) values exceeding 1 over broad carrier-concentration ranges at medium and high temperatures, with $\beta \text{−}{\mathrm{Bi}}_2{\mathrm{Se}}_2\mathrm{Te}$ reaching a peak $zT$ of 2.75. Our work demonstrates an effective optimization strategy within Janus tetradymite topological insulators and identifies Janus ${\mathrm{Bi}}_2{X}_{2}Y$ as promising thermoelectric candidates.

We present a theory of polarized photoluminescence of triplet excitons in semiconductor nanocrystal ensembles with the random fine structure contributed by the electron-hole exchange and carrier-nuclear hyperfine interactions. The interaction parameters are assumed to be normally and isotropically distributed. The exchange interaction is described by the Gaussian orthogonal ensemble of random matrices. The intensity of luminescence as well as the optical orientation and alignment are calculated as functions of the fine structure splitting parameters and the exciton lifetime. We have also analyzed the suppression of optical alignment and enhancement of optical orientation in an external longitudinal magnetic field.

We study fermionic and bosonic systems coupled to a real or synthetic static gauge field that is quantized, so the field itself is a quantum degree of freedom and can exist in coherent superposition. A natural source of a quantized magnetic flux (QMF) could be a superconducting current loop. We show that coupling to a common QMF gives rise to an emergent all-to-all interaction between particles with no classical analog, as it is topological and nonlocal (independent of interparticle distance). Moreover, the interaction persists via a quantized Aharonov-Bohm effect even when the particles lie in a nominally field-free region. The QMF mediates exchange of angular momenta between particles, and it gives rise to quantum phase transitions in both one- and two-dimensional systems, resulting in the spontaneous appearance of the chiral current and magnetic polarization. Many other interesting phenomena can be realized in this class of systems, for example, the noninteger Chern number when the magnetic flux exists in the quantum superposition of different flux states, or the nonlocal electron blockade. We show that similar physics can be realized in synthetic systems with artificial QMF, with the advantage of tunability enabling much higher strength of the synthetic QMF and the interaction of neutral particles.

We study intriguing dynamical features of hot Rubidium atoms driven by two light fields. The fields resonantly drive multiple Zeeman states within two hyperfine levels, yielding a cascaded-$\mathrm{\Lambda }$-like structure in the frequency space. A non-Hermitian Floquet tight-binding lattice with imaginary hopping between the nearest states effectively describes the coherence dynamics between Zeeman states within the ground hyperfine level. This emergent non-Hermitian dynamics is responsible for the generation of long-range coherence between the distant Zeeman states in the nonequilibrium steady state. By performing minimally invasive spin noise spectroscopy at strong driving intensity, we observe higher harmonic peaks in the coherent part of the power spectrum. Such sharp coherent peaks arise exclusively from long-range coherence between distant ground states via multiphoton transitions. Moreover, the peak amplitudes reveal an exponential decay of the coherence with increasing separation between the states.

We develop a first-principles framework for finite-temperature structural optimization that incorporates vibrational contributions to the free energy through anharmonic phonon theory. We extend and further improve the efficiency of the recent approach, enabling its application to systems in which the size of the primitive cell changes across structural phase transitions. Applying this framework to ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, we establish its pressure-temperature phase diagram and find that the slope of the phase boundary between the high-symmetry and low-symmetry phases is negative, with a magnitude of approximately $-60\mathrm{K}/\mathrm{GPa}$. The present results provide a theoretical foundation for discussing how changes in crystal symmetry influence the emergence of superconductivity.

We report dielectric spectroscopy of single-crystalline ${\text{NdMgAl}}_{11}{\text{O}}_{19}$, a magnetoplumbite hexaaluminate in which localized ${\text{Nd}}^{3+}$ moments coexist with a polarizable ${\text{AlO}}_5$ bipyramidal network. The real part of the permittivity ${\varepsilon }_c^{\prime }\left(T\right)$, measured along the crystallographic $c$ axis, increases as the temperature is lowered from 275 K to 30 K and is frequency-independent between 4 Hz and 50 kHz. At lower temperatures, a frequency-dependent decrease in permittivity is observed, followed by a further upturn below 2 K. The high-frequency ${\varepsilon }_c^{\prime }\left(T\right)$ is described by a Barrett formula supplemented by an effective two-level contribution, yielding a robust gap of $\mathrm{\Delta }=25.9\left(3\right)\mathrm{K}$ consistent with the lowest ${\text{Nd}}^{3+}$ crystal-electric-field (CEF) splitting. Below $\sim 30\mathrm{K}$, the dielectric response becomes strongly frequency and magnetic-field dependent. Isothermal ${\varepsilon }_c^{\prime }\left(H\right)$ measurements reveal a reproducible low-field crossover near ${\mu }_0{H}_c\simeq 0.85\mathrm{T}$, which we attribute to the competition between antiferromagnetic correlations and Zeeman splitting of the ground-state Kramers doublet. ${\text{NdMgAl}}_{11}{\text{O}}_{19}$ thus provides a Kramers reference system in which dielectric signatures of the excited-state CEF manifold can be distinguished from those of the field-tuned, correlation-dominated ground-state doublet in the centrosymmetric frustrated magnetoplumbite host.

The disorder operator, as an easily measured nonlocal observable, displays great potential in detecting intrinsic information of field theories. It has been systematically studied in one- and two-dimensional (1D and 2D) quantum systems, while the knowledge of 3D is still limited. The disorder operator associated with U(1) global symmetry exhibits rich geometric dependence on the shape of the spatial region at a quantum critical point, meanwhile, $(3+1)\mathrm{D}$ is the upper critical dimension for $O\left(N\right)$ criticality, both of which pose a challenge for exploring the disorder operator in high dimensions. In this Letter, we investigate the scaling behaviors of disorder operators in $(3+1)\mathrm{D}$ $O\left(3\right)$ models through a large-scale quantum Monte Carlo simulation combined with a theoretical analysis. Although the upper critical dimension introduces logarithmic corrections in correlations, we analytically prove and numerically demonstrate that the corrections do not modify the universal trihedral-corner contribution of the disorder operator. The universal contributions, such as the current central charge, have been revealed in our calculation, which establishes a concrete link between lattice simulations and continuum field theory. This work opens promising directions for the experimental and numerical exploration of universal properties at quantum critical points in $(3+1)\mathrm{D}$ models.

We develop a theory of drag in graphene double layers near charge neutrality. We work in the regime of electron hydrodynamics and account for interlayer correlations of charge puddle disorder. The drag resistivity is expressed in terms of the viscosity, intrinsic conductivity of the electron liquid, and the correlation function of the puddle disorder. The contributions of the interlayer transfer of momentum and energy to drag have opposite signs. This leads to a nonmonotonic dependence of the drag resistivity on the carrier density. For layer-symmetric doping, the drag resistivity changes sign as a function of the carrier density. At interlayer separations shorter than the disorder correlation length, the transconductivity saturates to the disorder-induced enhancement of the intralayer conductivity. We provide quantitative estimates of the effect for Dirac electron liquids in monolayer graphene and bilayer graphene double-layer devices.

We provide a quantum-mechanical description of the photoinduced dc current states and magnetic fields around nonmagnetic point impurities in a two-dimensional (2D) electron gas irradiated by a circularly polarized electromagnetic wave. Based on the solution of the corresponding time-dependent Schrödinger equation within the second-order perturbation theory in the electromagnetic wave amplitude, we find that the resulting dc magnetic field component perpendicular to the plane of the 2D system is distributed like in a set of random magnetic fluxes bound to the positions of impurities. As a result, the spatially averaged dc magnetic field does not vanish far from the sample edges and, thus, our scenario of the inverse Faraday effect in disordered systems differs strongly from the standard one based on the relaxation time approximation within the hydrodynamic or kinetic equation approaches which would give only the photoinduced currents flowing along the sample edges. The predicted mechanism for formation of rectified currents flowing around the impurity centers is shown to be generic both for 2D and 3D systems. The internal dc magnetic field can give rise to the photoinduced Hall effect and Faraday rotation for a probing electromagnetic signal.

Quantum antiscars characterized by the reduced wavefunction probability density along unstable periodic orbits have been a long-sought subject in the field of quantum chaos. In view of the antiresonance origin, an explicit spatial visualization of quantum antiscars at a single energy level remains still scarce in either theoretical proposals or experimental methods. Here we propose that antiscars can be directly visualized in energy-fixed local density of states (LDOS) spatial maps of electrostatically defined graphene quantum dots (GQDs), as a result of the leakage induced by Klein tunneling. Through systematic numerical simulations, quantum scars and antiscars are demonstrated to alternate between peaks and dips of the LDOS-energy spectrum, collectively following a relativistic equidistant recurrence. A mutual conversion between scars and antiscars can be also achieved by tuning an external magnetic flux. Our work opens horizons for understanding, detecting, and utilizing scarring and antiscarring phenomena in open quantum chaotic systems.

A novel solid solution, $\left(1-x\right)\mathrm{PbTi}{\mathrm{O}}_3-x\mathrm{TbFe}{\mathrm{O}}_3$ was investigated, with a specific composition of $\mathrm{x}=0.10$ exhibiting a giant negative coefficient of thermal expansion (CTE) of approximately $-68\times {10}^{-6}{}^{\circ }{\mathrm{C}}^{-1}$, with large volume contraction of about 2.5% over the temperature range $25-400{}^{\circ }\mathrm{C}$. The observed negative thermal expansion (NTE) magnitude surpasses that of other ${\mathrm{PbTiO}}_3$-based systems, being more than three times higher than pure ${\mathrm{PbTiO}}_3$. The enhanced NTE is linked to an anomalous change in the c-lattice parameter relative to the a-parameter, indicating structural modifications responsible for this behavior. Further, compositions within the range $0\le \mathrm{x}\le 0.10$ exhibit anomalous behavior in tetragonality retention, attributed to the combined influence of $\mathrm{P}{{\mathrm{b}}^{2+}}^{\prime }\mathrm{s} 6{\mathrm{S}}^2$ lone pair effect and strong Fe–O covalency, affecting structural stability.

We report a detailed structural and magnetic investigation of the spin-ladder compound ${\mathrm{Ba}}_2{\mathrm{CuTeO}}_6$ using neutron and synchrotron diffraction techniques, along with magnetic susceptibility measurements. High-resolution neutron and synchrotron powder diffraction reveal a structural phase transition from monoclinic $C$2/$m$ to triclinic $P\overline{1}$ symmetry below $\sim 275\mathrm{K}$, driven by octahedral distortions that alter the Cu-O-Te-O-Cu super-superexchange pathways. At low temperatures, ${\mathrm{Ba}}_2{\mathrm{CuTeO}}_6$ undergoes long-range antiferromagnetic ordering below the Néel temperature $T_N\approx 15\mathrm{K}$, confirmed by both powder and single-crystal neutron diffraction. The magnetic ordering is characterized by a commensurate propagation vector $\mathbf{k}=(0.5,0.5,0.5)$ and a reduced ordered moment of $\sim 0.48{\mu }_B$ per ${\mathrm{Cu}}^{2+}$ ion. These findings demonstrate that structural symmetry lowering modifies exchange anisotropy sufficiently to stabilize magnetic order in an otherwise low-dimensional system. These results establish ${\mathrm{Ba}}_2{\mathrm{CuTeO}}_6$ as a model platform for exploring dimensional crossover, exchange anisotropy, and structure-driven quantum magnetism in spin-ladder materials.

We analyze the magnetization curve of the spin-1/2 kagome Heisenberg model in a magnetic field. Using state-of-the-art variational wave functions based on neural networks, we confirm the presence of robust magnetization plateaus at $m=1/3$, $5/9$, and $7/9$ of the saturation value, stabilized by a spontaneous symmetry breaking of lattice translations with a $\sqrt{3}\times \sqrt{3}$ unit cell. Regarding the more challenging $m=1/9$ plateau, we find two competing valence bond crystals depending on the system size, both breaking translation as well as point group symmetries and with a larger $3\times 3$ unit cell. Such quantum states with local modulations of the magnetization average values could be observed experimentally in the near future.