We investigate the postquench dynamics of the quantum geometric tensor (QGT) of one-dimensional periodic systems with a suddenly changed Hamiltonian and make connections to physical observables. The diagonal component with respect to the crystal momentum gives a metric corresponding to the variance of the time-evolved position, and its coefficient of the quadratic term in time is the group-velocity variance, signaling ballistic wavepacket dispersion. The other diagonal QGT component with respect to time reveals the energy variance. The off-diagonal QGT component features a real part as a covariance and an imaginary part representing a quench-induced curvature. Using the Su-Schrieffer-Heeger model as an example, our numerical results of different quenches confirm that the postquench QGT is governed by physical quantities and local geometric objects from the initial state and postquench bands, such as the Berry connection, group velocities, and energy variance. Furthermore, the connections between the QGT and physical observables suggest the QGT as a comprehensive probe for nonequilibrium phenomena.

We investigate the phase diagram of a one-dimensional dissipative Bose-Hubbard model using the nonperturbative functional renormalization group (FRG). Each lattice site is coupled to an independent bath, generating long-range temporal interactions that encode non-Markovian dissipation. For a broad class of bath spectra (ohmic, subohmic, and superohmic) we identify two competing low-energy regimes: a Luttinger-liquid line of fixed points and a dissipative fixed point characterized by finite compressibility, vanishing superfluid stiffness, and universal scaling exponents, separated by a Berezinskii-Kosterlitz-Thouless transition. The FRG framework is essential here, as it provides access to the complete renormalization group flow and all fixed points from a single microscopic action, beyond the reach of perturbative or variational methods. This work establishes a unified and systematically improvable framework for describing dissipative quantum phases in one dimension.

While the Mg-Si system features only one thermodynamically stable compound, $\mathrm{M}{\mathrm{g}}_2\mathrm{Si}$, at ambient pressure, multiple new phases emerge under compression up to ∼100 GPa. Intriguingly, above 500 GPa, $\mathrm{M}{\mathrm{g}}_2\mathrm{Si}$ reemerges as the sole stable compound. In this work, we combine adaptive genetic algorithm crystal-structure prediction with machine learning interatomic potentials to systematically explore high-pressure stability of Mg-Si system at 200, 300, and 400 GPa. By constructing a pressure–composition phase diagram spanning 100 to 500 GPa, we identify several pressure-stabilized phases, $Cmmm \mathrm{M}{\mathrm{g}}_4\mathrm{S}{\mathrm{i}}_3$ and $R\overline{3}m \mathrm{M}{\mathrm{g}}_3\mathrm{Si}$, which exhibit unexpected stoichiometries and structural motifs. Through analysis of electronic structure, we demonstrate that the localization of electrons and their bonding character play a crucial role in the phase stability and structural evolution under high pressure. These findings suggest that Mg-Si compounds with diverse compositions could form in oxygen-deficient planetary interiors, and provide an extended structural database for exploring multicomponent systems containing Mg and Si under extreme conditions.

We report observations of one-dimensional neutron diffraction from highly oriented pyrolytic graphite (HOPG), where the scattering angle varies continuously with incident angle following classical grating-like behavior. The 2D polycrystalline structure of HOPG—with highly aligned layers along the $c$ axis but random in-plane rotations—creates planes of scattering intensity in reciprocal space at $Q_c=n(2\pi /d)$ where $d=3.35\AA$ is the interlayer spacing. As the Ewald sphere sweeps through reciprocal space during sample rotation, it continuously intersects these planes, producing the observed angular dispersion. We observe both first-order ($n=1$) and second-order ($n=2$) diffraction at conventional scattering angles (${25}^{\circ }–{70}^{\circ }$), with peak positions that remain temperature-independent between 10 K and 294 K and follow quantitative agreement with momentum conservation $Q_c=k[sin\psi -sin{\psi }_f]=n(2\pi /d)$. X-ray diffraction under similar conditions shows no comparable behavior, confirming that sharp nuclear-vacuum contrast is essential. While diffraction intensities are weak ($\sim {10}^{-6}$ of Bragg peaks), the observations demonstrate how the interplay of atomic-scale periodicity, nuclear contrast, and structural disorder enables observation of continuous diffraction curves at thermal neutron wavelengths, illustrating how HOPG's unique microstructure determines its scattering properties beyond conventional Bragg diffraction.

High-pressure experiments using diamond anvils have revealed unique properties and phase behavior of ${\mathrm{H}}_2\mathrm{O}$ under extreme conditions. When contained in diamond-anvil cells, the ${\mathrm{H}}_2\mathrm{O}$ samples are usually in direct contact with the diamond anvil. However, the extent to which this interface affects measured pressure-induced properties and behavior, including coexistence lines of ice phases, remains unknown. Combining artificial neural network methods and active learning schemes with large-scale molecular dynamics simulations, we elucidate the interfacial effects on various properties of high-pressure ice phases, including superionic states, solid-solid phase transitions, and melting. The results reveal that the presence of this interface can significantly lower the hydrogen superionic transition temperature. Remarkably, the interface can also induce a spontaneous transition from bcc- to fcc-based ice following the inverse Bain mechanism. Further, we redefined a stability field of bcc and fcc ice below the melting line and predicted the existence of fcc ice at much lower pressures than previously thought. More broadly, the results emphasize the importance of interface effects in understanding a wide range of phenomena reported in experimental studies of ice under pressure, including inconsistencies between theoretical and experimental results of this fundamental system.

The rare-earth orthoferrite family is prototypical strongly correlated systems, known for its highly tunable ferromagnetism properties. Among these materials, $\mathrm{S}{\mathrm{m}}_{0.5}{\mathrm{Y}}_{0.5}\mathrm{Fe}{\mathrm{O}}_3$ exhibits potential for applications becaue of its near room temperature spin reorientation transition. However, a comprehensive understanding of the spin reorientation and structural phase transitions in $\mathrm{S}{\mathrm{m}}_{0.5}{\mathrm{Y}}_{0.5}\mathrm{Fe}{\mathrm{O}}_3$ under pressure remains unclear. In this work, we present spectral (Raman and synchrotron x-ray diffraction) and electrical (electrochemical impedance spectroscopy) evidence of spin reorientation and an isostructural phase transition in $\mathrm{S}{\mathrm{m}}_{0.5}{\mathrm{Y}}_{0.5}\mathrm{Fe}{\mathrm{O}}_3$ up to 50 GPa. DFT calculations demonstrate that. while $\mathrm{S}{\mathrm{m}}_{0.5}{\mathrm{Y}}_{0.5}\mathrm{Fe}{\mathrm{O}}_3$ retains its semiconducting behavior under pressure, it undergoes a pressure-induced spin reorientation transition, with the magnetic easy axis switching from the (100) to the (001) direction. These findings establish pressure as a critical parameter for tuning correlated-electron behavior in $\mathrm{S}{\mathrm{m}}_{0.5}{\mathrm{Y}}_{0.5}\mathrm{Fe}{\mathrm{O}}_3$, paving the way for applications in spintronic and next-generation quantum transportation devices.

Wüstite (FeO), silica (${\mathrm{SiO}}_2$), and water (${\mathrm{H}}_2\mathrm{O}$) are highly abundant in the interior of planets. Given their extensive participation in most geochemical reactions within the mantle of Earth and other planets, it is important to investigate the high-pressure compounds of the ternary $\mathrm{FeO}\text{−}{\mathrm{SiO}}_2\text{−}{\mathrm{H}}_2\mathrm{O}$ system. Here, taking advantage of machine learning assisted crystal structure predictions based on DFT+U calculations, we identified two thermodynamically stable iron hydrosilicate phases, the $\alpha \text{−}{\mathrm{FeSiO}}_4{\mathrm{H}}_2$ and $\beta \text{−}{\mathrm{FeSiO}}_4{\mathrm{H}}_2$ at high pressures of 50–150 GPa and above 150 GPa, respectively. Both these structures exhibit superionic behavior at pressure-temperature conditions corresponding to the Earth's interior. Most importantly, as a reservoir of water, the ${\mathrm{FeSiO}}_4{\mathrm{H}}_2$ can enter the lower mantle and release water through the disproportionation of ferrous iron, which occurs during the accretion process. Our findings provide a different perspective on the behavior of the Earth's interior and expose more possibilities for the evolution models of terrestrial planets in our solar system and beyond.

Universal time-temperature scaling of conductivity spectra in disordered solids has been explained by thermally activated hopping of noninteracting particles over random energy barriers. An open problem is whether the random barrier model accounts for site energy disorder in real materials. Through mapping many-particle hopping in a disordered site energy landscape to that of independent particles in a barrier landscape, we show that time-temperature scaling is correctly described by the associated barrier model in the low temperature limit. However, the site energy model displays good scaling behavior at substantially higher temperatures than the barrier model, in agreement with experimental observations. Extending the mapping to account for different types of mobile ions in disordered solid electrolytes allows us to understand why time-temperature superposition can be absent in mixed alkali glasses.

Complex fluids such as water exhibits many anomalous phenomena, and research suggests these properties are closely tied to critical fluctuations near the liquid-liquid phase transition critical point (LLCP). However, whether a similar LLCP exists in metallic glass-forming liquids, which are notable for their high atomic coordination, remains an open question. Although dynamic anomalies such as the breakdown of the Stokes-Einstein (SE) relation have often been attributed to dynamic heterogeneity or structural changes, relatively few studies have analyzed these anomalies from a thermodynamic-fluctuation perspective. This gap probably stems from the challenges in detecting density-driven phase transitions in such systems. Here, we use numerical simulations to explore the thermodynamic mechanisms behind dynamic anomalies in a prototypical metallic glass-forming melt. We observe substantial thermodynamic fluctuations near a particular region, which likely corresponds to a frustration state of liquid, vapor, and glass. These fluctuations may contribute to the violation of the SE relation. Our findings offer a fresh Griffiths-like perspective on the dynamic anomalies seen in supercooled metallic liquids, and shed light on their underlying mechanisms.

We study the Lanczos coefficients in a quadratic model given by an impurity interacting with a multimode field of fermions, also known as the resonant level model. We analytically derive closed expressions for the Lanczos coefficients of Majorana fermion operators of the impurity for different structures of the coupling to the hybridization band at zero temperature. While the model remains quadratic, we find that the growth of the Lanczos coefficients structurally depends strongly on the chosen coupling. Concretely, we find (i) approximately constant, (ii) exactly constant, (iii) square-root-like, as well as (iv) linear growth in the same model. We further argue that in fact through suitably chosen couplings, essentially arbitrary Lanczos coefficients can be obtained in this model. These altogether evince the inadequacy of the Lanczos coefficients as a reliable criterion for classifying the integrability or chaoticity of the systems. Eventually, in the wideband limit, we find exponential decay of autocorrelation functions in all the settings (i)–(iv), which demonstrates the different structures of the Lanczos coefficients not being indicative of different physical behavior.

An edge bit in an average symmetry protected topological mixed state (ASPT) is studied. The state is protected by one strong $Z_2$ symmetry and one weak (average) $Z_2$ symmetry. As analogous objects of pure symmetry protected topological states, the ASPT possesses edge bits. In particular, the analogous operator response, that is, symmetry fractionalization, exists. The fractionalization preserves the presence of the ASPT in the bulk and the fractionalized edge operators acting on the edge bits of the ASPT. In this work, based on the cluster model and by employing Choi map, we discuss generic features of the edge bits and numerically clarify the behavior of the edge bits and their robustness for varying decoherence and perturbative interactions. By using operator space mutual information, we track the flow of quantum correlations between the two edges. Remarkably, even in the ASPT regime, a finite portion of the initial edge-to-edge correlation survives.

We report a comprehensive experimental and theoretical study of the anomalous Hall and Nernst effects in (001)-oriented epitaxial MnAlGe thin films. First-principles calculations of intrinsic anomalous Hall conductivity originating from Berry curvature $\left({\sigma }_{xy}^{int}\right)$ predict a large value, $\sim 856{\mathrm{S}\mathrm{cm}}^{-1}$, at 0 K and gradual reduction with temperature. Experimentally measured anomalous Hall conductivity is also large value, $\sim 670{\mathrm{S}\mathrm{cm}}^{-1}$, at 10 K but exhibits almost three times stronger reduction with temperature than the theoretical prediction. Large positive and negative values of anomalous Nernst conductivity $\left({\alpha }_{xy}^{int}\right)$ near the Fermi level were predicted at 300 K: $+3.8{\mathrm{A}\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ at 78 meV and $-3.0{\mathrm{A}\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ at $-34$ meV, respectively. Experimentally evaluated anomalous Nernst conductivity ${\alpha }_{xy}^A$ shows a significant reduction in magnitude and a sign reversal with increasing temperature, $1.09\pm 0.01$ ${\mathrm{A}\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ at 75 K to $-0.12\pm 0.01$ ${\mathrm{A}\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ at 300 K, which cannot be explained by giving any chemical potential shift based on present theoretical calculations. These discrepancies suggest that the conventional theoretical approach to calculate ${\sigma }_{xy}^{int}$ and ${\alpha }_{xy}^{int}$, commonly employed in previous studies, is insufficient to explain the anomalous Hall effect and anomalous Nernst effect observed in MnAlGe. Through examination of various possible origins, our analysis points to thermally induced spin fluctuations, likely amplified by the quasi-two-dimensional structure of MnAlGe, as the most plausible source of unique temperature dependence of ${\sigma }_{xy}^A$ and ${\alpha }_{xy}^A$ through their influence on either intrinsic or extrinsic contributions. This interpretation is supported by the observation of a pronounced magnon-induced magnetoresistance effect, which directly reveals a much stronger spin-fluctuation impact on transport in MnAlGe compared to conventional three-dimensional ferromagnets.

Exploring sign structures of quantum wave functions attracts considerable attention due to the potential for advances in modeling complex phases of matter. This stimulates the development of different optimization procedures for imitating and manipulating the sign structures of quantum states. In this work, utilizing a brute force approach based on a set of single-qubit transformations, we evaluate protocols enabling positivization of the one-dimensional $J_1-J_2$ model ground states in the regime of strong frustration. Based on the obtained positivization results, we show the difference between the cases of periodic and open boundary conditions, and also establish the dependence of the sign structure on parity of the simulated spin chains.

${\mathrm{Cr}}_{1+x}{\mathrm{Te}}_2$ is a self-intercalated van der Waals system that is of current interest for its room-temperature room-temperature ferromagnetic (FM) phases and tunable topological properties. In bulk samples, the strain from the interstitial Cr ions leads to distinct structural phases for different ranges of $x$. Early neutron powder diffraction (NPD) measurements on the monoclinic phase ${\mathrm{Cr}}_3{\mathrm{Te}}_4$ ($x=0.5$) presented evidence for competing FM and antiferromagnetic (AFM) phases. Here we apply neutron diffraction to a single crystal of ${\mathrm{Cr}}_{3+\delta }{\mathrm{Te}}_4$ with $\delta =-0.10$ and discover that it consists of two distinct monoclinic phases, one with FM order below $T_{\mathrm{C}}\approx 321$ K and another that develops AFM order below $T_{\mathrm{N}}\approx 86$ K. In contrast, we find that a crystal with $\delta =-0.26$ exhibits only FM order below $T_{\mathrm{C}}\approx 285$ K. The single-crystal analysis is complemented by results obtained with NPD, x-ray powder diffraction, and transmission electron microscopy (TEM) measurements on the $\delta =-0.10$ composition. From observations of spontaneous magnetostriction of opposite sign at $T_{\mathrm{C}}$ and $T_{\mathrm{N}}$, along with the TEM evidence for both monoclinic phases in a single thin ($\approx 100$ nm) grain, we conclude that the two phases must have a fine-grained ($\lesssim 100$ nm) intergrowth character, as might occur from high-temperature spinodal decomposition during the growth process. Calculations of the relaxed lattice structures for the FM and AFM phases with density functional theory provide a rationalization of the observed spontaneous magnetostrictions. Correlations between the magnitude and orientation of the magnetic moments with lattice parameter variation demonstrate that the magnetic orders are sensitive to strain, thus explaining why magnetic ordering temperatures and anisotropies can be different between bulk and thin-film samples, when the latter are subject to epitaxial strain. Our results point to the need to investigate the supposed coexistence FM and AFM phases reported elsewhere in the ${\mathrm{Cr}}_{1+x}{\mathrm{Te}}_2$ system, such as in the ${\mathrm{Cr}}_5{\mathrm{Te}}_8$ phase ($x=0.25$).

The integration of ferroelectric (FE) and antiferromagnetic (AFM) orders in two-dimensional (2D) materials provides a promising avenue for the nonvolatile control of coupled spin and valley degrees of freedom, a capability central to advancing spin-valleytronics. However, realizing a single material system where these quantum states can be independently and reversibly manipulated by distinct stimuli, a prerequisite for multifunctional devices, has remained elusive. Here, we demonstrate a dual-switch mechanism in bilayer $\mathrm{V}{\mathrm{S}}_2$, a room-temperature FE-AFM system, that enables electrical and magnetic control of a layer-locked anomalous valley Hall effect (AVHE). First-principles calculations reveal that interlayer sliding breaks spatial inversion symmetry, inducing a switchable out-of-plane FE polarization that coexists with interlayer AFM. The spin-orbit coupled valley polarization can be reversibly switched either by FE polarization reversal or by a magnetic-field-induced spin-flip transition, confirming the existence of electrically and magnetically addressable valley states. The Berry curvature exhibits both valley-contrasting and layer-locked characteristics, which underpin a switchable Hall response. Notably, electric and magnetic switching are functionally equivalent in modulating valley, layer, and spin indices, revealing strong magnetoelectric coupling. This work establishes a multidegree-of-freedom operational paradigm in 2D multiferroics and opens a viable design pathway toward multistate memory and spin-valleytronic logic devices.

Optical and magneto-optical properties of magnetic materials have been widely exploited to characterize magnetic structures and phenomena; however, their temperature dependence is not well understood. This study implements the supercell approach with thermal lattice and magnetic disorders to obtain optical and magneto-optical spectra at finite temperatures based on the Williams-Lax theory. Our results show that large optical spectrum signals are generated at photon energies below 1 eV, originating from the phonon- and magnon-assisted intraband transitions as lattice and magnetic temperatures increase. In addition, the prominent peak near 2.7 eV is redshifted proportionally to magnetic temperature but depends much less on lattice temperature. By analyzing unfolded bands, we show that the reduction of exchange splitting due to the thermal demagnetization causes this redshift. Our unfolded electronic band structure with magnetic disorder shows band kinks, which are characteristic evidence of the coupling between electrons and magnetic excitations. First-order magneto-optical spectra at finite temperatures are also predicted, but due to their small magnitude, they suffer more from sampling errors. We discuss the effect of zero-point vibrations and the connection of these simulations to the Drude model for intraband transitions.

In the emerging field of two-dimensional (2D) intrinsic magnetic materials, the Dzyaloshinskii-Moriya interaction (DMI) has attracted wide attention for its crucial role in triggering exotic spin textures, provided that the Heisenberg exchange supplies the long-range magnetic order as a background. In this work, we predict that DMI alone can stabilize 2D long-range magnetism at finite temperatures. As a representative model, we propose a three-spin lattice considering only DMI, and analytically derive a twofold-degenerate long-range order, exhibiting both out-of-plane ferromagnetism and in-plane ${120}^{\circ }$ antiferromagnetism, which we term Dzyaloshinskii-Moriya magnetism (DMM). Using first-principles calculations combined with spin-wave spectrum calculations and Monte Carlo simulations, we predict that monolayer $\mathrm{Li}\text{−}{\left({\mathrm{IrI}}_3\right)}_2$ is a promising candidate for hosting such DMM, featuring a spin-wave excitation gap of 1.70 meV and a critical temperature of 2.61 K. Interestingly, the dynamics of chiral domain walls in the DMM are nearly frozen below $\sim 0.1$ K, which enables artificial imprinting of specific domain patterns. These findings expand the scope of 2D magnetism and open a unique avenue for DMI-based spintronics.