The glass transition represents a long-standing enigma in condensed matter physics and materials science. Traditionally, this transition, often associated with α relaxation, is viewed as a thermally activated process. In this study, by integrating molecular dynamics simulations and experimental verification, we revealed that static loading can effectively reduce the glass transition temperature in the out-of-equilibrium glassy state, exhibiting a distinct stress-temperature equivalence compared to that observed under dynamic loading in the equilibrium liquid state. This indicates that mechanical energy can effectively substitute thermal energy in facilitating the glass transition. At the microscopic level, the application of static load enhances atomic mobility, triggering cooperative atomic movements and fostering the development of “faster-atom” networks, which ultimately facilitate the global motion of numerous atoms necessary for the glass transition. These findings highlight the significance of static load in tailoring the structure and dynamics of metallic glasses.

Fredkin-type kinetic constraints appear in systems ranging from classical interfaces to th e Fredkin and Motzkin quantum spin chains. Here, we identify a pseudolocal conserved charge associated with Fredkin-constrained dynamics that may be leveraged to subdiffusively bound the dynamical exponent $z\ge 5/2$. Our results establish that transport in Fredkin-constrained systems belongs to a distinct dynamical universality class that is separate from ordinary diffusion. This universality class is stable to local perturbations that conserve the pseudolocal charge.

Single-atom magnet (SAM) represents the single bit with ultimate atomic-scale limit in the field of magnetic storage and spintronics. Large magnetic reversal barrier and long magnetic lifetime of SAM are vitally important for its application to single-atom magnetic memory, which is intensely related to the spin dynamics induced by spin-vibration coupling (SVC) between magnetic adatom and substrate. In this work, we investigated the static magnetic energy level, relaxation pathway, SVC interaction, spin dynamics, and magnetization relaxation rate combined with the density functional theory method and crystal field model Hamiltonian analysis as well as ab initio calculations. The static relaxation pathway reveals an effective magnetization reversal barrier ($U_{\mathrm{eff}}$) of 92.1 meV, much higher than the experimental excitation energy of 7.7 meV, which is due to the abundant intermediate SVC-induced spin-vibration states between the ground and first excited magnetic states, especially the state caused by vibrational mode $\hslash \omega =7.56\mathrm{meV}$, opening a fast relaxation channel for magnetization reversal. The quantum tunneling of magnetization (QTM) event is the primary cause of magnetization reversal in the temperature of $1–6\mathrm{K}$, with an estimated QTM relaxation time ($\tau$) of 0.02 s. The spin dynamics demonstrates that the Raman regime is the dominant relaxation mechanism at $6–50\mathrm{K}$, and the relaxation rates in $6–10\mathrm{K}$ almost completely contribute from the two-mode Raman transitions involving vibrational modes of 4.71 and 7.56 meV. The predicted magnetic blocking temperature ($T_{\mathrm{B}}$) of $1.5–17\mathrm{K}$ indicates that the U@MgO system exists a loop hysteresis in this temperature, exhibiting a characteristic SAM behavior. Our SVC calculations suggest that the fast relaxation in U@MgO system can be suppressed by weakening or quenching the SVC interaction for the low-energy vibrational modes. The quantitative predictions of relaxation rate and magnetic blocking temperature provide a guidance on the future magnetic measurements.

We have investigated the quasi-one-dimensional Ni-chain compound ${\mathrm{PbMn}}_2{\mathrm{Ni}}_6{\mathrm{Te}}_2{\mathrm{O}}_{18}$ using theoretical DFT calculations, inelastic neutron scattering, and optical spectroscopy in order to understand the nature of magnetic exchange interactions. Our inelastic neutron scattering study at 5 K on a powder sample reveals two bands of magnetic excitations, the first near 8 meV and the second near 18 meV originating from the antiferromagnetic zone center near $Q=1$ Å. On the other hand, at 100 K (which is above ${\mathrm{T}}_N=86$ K) a broad diffuse scattering signal is observed indicating the presence of short range magnetic correlations. We have analyzed the magnetic excitations based on the Linear Spin Wave Theory (LSWT) and compared the experimentally estimated exchange parameters with the DFT calculations. Our analysis reveals that the value of the exchange parameter at the larger distance ($\mathrm{d}=3.654\AA$) $J_3=4.21\left(8\right)$ meV between Ni-Ni (from interchain) is the strongest amongst the allowed six exchange parameters, which suggests that this system is not really a quasi-one-dimensional and confirmed by the absence of a Haldane gap. We have also presented the electronic structure calculations. The spin-polarized partial density of states (DOS) projected onto the Mn-d and Ni-d orbitals reveals that the $\mathrm{Ni}\text{−}{\mathrm{d}}_{x^2-y^2}$ contribution is dominant below the Fermi level in the spin-up and spin-down channel, while a minimal contribution from spin-up Mn states in the occupied region, suggesting a nearly high-spin state. The estimated Néel temperature, based on experimental exchange parameters is found to be in close agreement with the experimental value.

The origin of the magnetic quadrupole (MQ) interactions in ${\mathrm{Gd}}_3{\mathrm{Ru}}_4{\mathrm{Al}}_{12}$, which is known as a frustrated spin system and as a host material for skyrmion with a centrosymmetric crystal structure, are discussed. The MQ interactions between ferromagnetic (FM) spin trimers with imperfect FM directivity are deduced from a synthesis of dipole Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. The Hamiltonian, which includes both the MQ interactions and dipole interactions is proposed, and magnetic anisotropies, magnetic phase transitions, and the contribution of the MQ interactions to stabilize the skyrmion lattice (SkL) are discussed based on this Hamiltonian. Degrees of MQ freedom carried by the trimers contribute to stabilizing the SkL which appears at finite temperatures.

Hard x-ray angle-resolved photoemission spectroscopy reveals significant changes in the valence band states of ${\mathrm{EuPd}}_2{\mathrm{Si}}_2$ at a temperature $T_V$, where the Eu ions undergo a temperature-induced valence crossover from a magnetic ${\mathrm{Eu}}^{2+}$ state to a low-temperature valence-fluctuating state. The substitution of Pd by Au and Si by Ge results in a decrease in $T_V$ and the emergence of an antiferromagnetic state at low temperatures without valence fluctuations. It has been proposed that the boundary between the antiferromagnetic order and the valence transition represents a first-order phase transition associated with a specific type of second-order critical endpoint. In this scenario, strong coupling effects between fluctuating charge, spin, and lattice degrees of freedom are to be expected. In the case of ${\mathrm{EuPd}}_2{\left({\mathrm{Si}}_{1-x}{\mathrm{Ge}}_x\right)}_2$ with $x=0.13$, which is close to the critical endpoint, a splitting of conduction band states and the emergence of flat bands with a restriction along the $\mathrm{\Gamma }$-X directions have been observed. A comparison with ab initio theory shows a high degree of agreement with the experimental results.

In the intermetallic rare-earth tetragonal ${\mathrm{EuAl}}_4$ system, competing itinerant exchange mechanisms lead to a complex magnetic phase diagram, featuring a centrosymmetric skyrmion lattice. Previous inelastic x-ray scattering (IXS) experiments revealed that the incommensurate charge-density wave (CDW) transition in ${\mathrm{EuAl}}_4$ ($T_{\text{CDW}}=142\mathrm{K}$) is driven by momentum-dependent electron-phonon coupling (EPC). We present the results of IXS under high hydrostatic pressure induced by diamond anvils and show how the EPC in ${\mathrm{EuAl}}_4$ is renormalized and suppressed in the material's temperature-pressure phase diagram. Our findings highlight the crucial role of momentum-dependent EPC in the formation of the CDW in ${\mathrm{EuAl}}_4$ and provide further insights into how external pressure can be used to tune charge ordering in quantum materials.

Supervised and unsupervised machine-learning-based frameworks have been implemented in the past to classify various dynamical phases of disordered quantum systems using rather sophisticated (highly preprocessed or difficult to generate) input data. In this paper, we begin by questioning the existence of a nonergodic extended phase, namely, the many-body critical (MBC) phase in finite systems of an interacting quasiperiodic system. We find that this phase can be separately detected from the other phases, such as the many-body ergodic (ME) and many-body localized (MBL) phases, in the model through supervised neural networks made for both binary and multiclass classification tasks, utilizing, rather unpreprocessed, eigenvalue spacings and eigenvector probability densities as input features. Moreover, the output of our trained neural networks can also indicate the critical points separating ME, MBC, and MBL phases, which are consistent with the same obtained from other conventional methods. We also employ unsupervised learning techniques, particularly principal component analysis (PCA) of eigenvector probability densities, to investigate how this framework, without any training, captures the, rather unknown, many-body phases (ME, MBL, and MBC) and single-particle phases (delocalized, localized, and critical) of the interacting and noninteracting systems, respectively. Our findings reveal that PCA entropy serves as an effective indicator (order parameter) for detecting phase transitions in the single-particle systems. Moreover, this method proves applicable to many-body systems when the data undergoes a suitable preprocessing. Interestingly, when it comes to the extraction of critical (correlation length) exponents through a finite-size scaling, we find that for single-particle systems, scaling collapse of neural network outputs is obtained using components of inverse participation ratio (IPR) as input data. Remarkably, we observe identical critical exponents as obtained from the scaling collapse of the IPR directly for different single-particle phase transitions. However, the current finite-size scaling approach to the network output cannot reliably extract critical exponents for the many-body system that needs further investigation.

Periodically driven systems have a longstanding reputation for establishing rich topological phenomena beyond their static counterpart. In this work, we propose and investigate a periodically driven extended Su-Schrieffer-Heeger model with three sites per unit cell, obtained by replacing the Pauli matrices with their $3\times 3$ counterparts. The system is found to support a number of edge modes over a range of parameter windows, some of which have no static counterparts. Among these edge modes, of particular interest are those which are pinned at a specific quasienergy value. Such quasienergy-fixed edge modes arise due to the interplay between topology and chiral symmetry, which are typically not expected in a three-band static model due to the presence of a bulk band at the only chiral-symmetric energy value, i.e., zero. In our time-periodic setting, another chiral-symmetric quasienergy value exists at half the driving frequency, which is not occupied by a bulk band and could then host chiral-symmetry-protected edge modes ($\pi$ modes). Finally, we verify the robustness of all edge modes against spatial disorder and briefly discuss the prospect of realizing our system in experiments.

In this work, we study an interacting tight-binding model of magic-angle twisted bilayer graphene (MATBG) with a twist angle of $1.{05}^{\circ }$. We derive effective theories based on a mean-field normal state at charge neutrality, thereby including the renormalizations coming from integrating out high-energy modes. In these theories, the flat bands display a sizable increase of the bandwidth, suggesting the renormalization of the magic angle. Additionally, the corresponding wave functions flow towards the limit of perfect particle-hole symmetry and sublattice polarization (the “chiral” limit). We further represent the flat bands in the “vortex Chern” basis and discuss the implications on the dynamics, regarding the “flat” and chiral symmetries of MATBG, as manifested in the symmetry-broken states at neutrality.

Kagome lattices, characterized by unique band structures such as flat bands and van Hove singularities, serve as a compelling platform for exploring the interplay between electronic states such as charge density waves, superconductivity, and topological quantum phenomena. In this study, we employed high-resolution angle-resolved photoemission spectroscopy and first-principles calculations to systematically characterize the distinct surface terminations of cleaved single-crystal ${\mathrm{CsTi}}_3{\mathrm{Bi}}_5$ and elucidate their corresponding band structures, providing critical insights into their intrinsic electronic states. Our findings reveal a pronounced splitting of flat bands on Bi-terminated surfaces, which is absent on Cs-terminated surfaces, indicating distinct surface electronic environments. Notably, the coexistence of original and replicated flat bands points to intricate interfacial interactions, potentially involving phenomena such as charge order, localized orbital hybridization, or surface reconstruction, rather than a straightforward rigid band shift. We find this behavior is attributed to a localized charge-driven hole doping effect at the interface, as supported by theoretical simulations and the observed modulation in band dispersions. These insights deepen our understanding of electronic structure modulation in kagome materials, paving the way for targeted band engineering and the investigation of emergent quantum phenomena such as unconventional superconductivity and topological orders.

We investigate quantum phase transitions in a topological Josephson junction with an embedded ferromagnetic layer, revealing a rich landscape of critical phenomena. The low-energy excitations comprise Majorana fermions propagating along the junction, coupled to the magnons in the ferromagnet. Based on mean-field and renormalization group arguments, we predict Berezinskii-Kosterlitz-Thouless (BKT) transitions in this system, both in the case of a magnetic easy-plane and weak easy-axis anisotropy. In the latter case, this is based on an emergent effective easy plane, spanned by the easy axis and the component of the magnetization, which couples to the Majoranas. We conclude by presenting a conjecture for the full phase diagram of the model. It covers BKT transitions as well as exotic multicritical and supersymmetric points known from related models of interacting real fermions and bosons.

Noncollinear antiferromagnets (AFMs) have the advantages of negligible stray fields and fast spin dynamics in potential spintronic applications. Investigations have been dedicated to the switching of magnetic moment in noncollinear antiferromagnets. However, it remains challenging to manipulate the transition between collinear and noncollinear orders, which have a significant impact on transport properties such as large anomalous Hall effect. Here, using density functional theory calculation and Monte Carlo simulations, we report electrically tunable transition between collinear and noncollinear antiferromagnetic orders in the two-dimensional Cr intercalated multiferroic ${\left(\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3\right)}_2\mathrm{C}{\mathrm{r}}_2$. Arising from the coupling of ferroelectric polarization and magnetic properties as well as the symmetry of intercalated architecture, the Dzyaloshinskii-Moriya interaction can be electrically modulated. Intercalated ${\left(\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3\right)}_2\mathrm{C}{\mathrm{r}}_2$ shows a transition between a trivial collinear AFM and a nontrivial noncollinear AFM order harbored skyrmion lattice when the polarization state of $\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$ is switched. Furthermore, the variation of magnetic configuration under different temperatures are investigated in the multiferroic intercalated system, and the melting process of AFM skyrmion lattice is revealed. These findings offer a general approach for the manipulation of noncollinear AFM orders for future spintronics.

Exceptional point (EP) is the singularity of a non-Hermitian system with the simultaneous coalescence of both eigenvalues and eigenvectors. This concept is often discussed in systems with local potentials. It has been widely believed that the balanced gain and loss respects the parity-time $\left(\mathcal{PT}\right)$ symmetry, and thus dictates the emergence of EPs. Here, we challenge this notion by examining, without loss of generality, the magnon spectrum in ferromagnetic bilayers coupled by dipole-dipole interactions. By separating the nonlocal dipolar field into volume and surface parts, we find that the volume term respects the $\mathcal{PT}$ symmetry while the surface term generally does not. Indeed, we observe EPs for both forward and backward volume magnons, but not for the Damon-Eshbach (DE) surface magnon. We show that, unlike the volume modes, the nonreciprocity (or chirality) of the DE mode results in an asymmetrical distribution of the magnon wave function across the magnetic bilayer, which breaks the $\mathcal{PT}$ symmetry and thus prevents the emergence of EPs. Our results highlight the key role of dipolar interaction in the formation of magnonic EPs, and can be readily generalized to other systems governed by nonlocal interactions.

Strong zero modes are edge-localized degrees of freedom capable of storing information at infinite temperature, even in systems with no disorder. To date, their stability has only been systematically explored at the physical edge of a system. Here we extend the notion of strong zero modes to the boundary between two systems and present a unifying framework for the stability of these boundary strong zero modes. Unlike zero-temperature topological edge modes, which are guaranteed to exist at the interface between a trivial and topological phase, the robustness of boundary strong zero modes is significantly more subtle. This subtlety is perhaps best illustrated by the following dichotomy: we find that the interface between a trivial and ordered phase does not guarantee the existence of a strong zero mode, while the interface between two ordered phases can, in certain cases, lead to an exact strong zero mode.

We investigate the multiparticle ring exchange couplings of the two-dimensional triangular Wigner crystal in external commensurate triangular and honeycomb potentials using a semiclassical approach that is valid in the regime where Coulomb interactions dominate over electronic kinetic energy. In this limit, increasing the strength of the potential drives a transition from a ferromagnet to a ${120}^{\circ }$ Néel antiferromagnet for both types of external potentials. In the triangular case, we find that the transition occurs already for a weak potential, whereas in the honeycomb case, it occurs when the potential is nearly two orders of magnitude larger. Our results are relevant to the magnetism of generalized Wigner crystal phases observed at certain rational fillings of the moiré superlattice in transition-metal dichalcogenide heterobilayers.

Molybdenum dioxide $\left({\mathrm{MoO}}_2\right)$, which crystallizes in a distorted rutile-type monoclinic $(P{2}_1/c)$ structure, is a promising material for applications in electrocatalysis, photocatalysis, lithium-ion batteries, and supercapacitors. Understanding its structural evolution under high pressure is essential for constructing a comprehensive phase diagram and tuning the properties of transition metal oxide systems. In this study, we systematically investigate the structural and electronic behavior of ${\mathrm{MoO}}_2$ under high pressure using Raman spectroscopy, synchrotron x-ray diffraction, electrical transport measurements, and first-principles calculations. Our results reveal two successive phase transitions: from the pristine monoclinic phase to a distorted monoclinic (M′, $P{2}_1/c$) phase near 10 GPa, and subsequently to an orthorhombic (Pbca) phase above 30 GPa. This structural evolution is accompanied by a pronounced change in electronic transport, marked by a transition from metallic to semiconductorlike behavior. Structure prediction and density functional theory calculations confirm the stability of the Pbca phase above ∼31 GPa and reveal its narrow-gap semiconducting character. These findings establish a direct link between structural transitions and electronic properties in ${\mathrm{MoO}}_2$ under compression, offering valuable insight into the pressure-tunable behavior of transition metal oxides.

Skyrmions—topologically nontrivial magnetic quasiparticles—can emerge in two-dimensional chiral magnets due to moderate or high strength of the Dzyaloshinskii-Moriya (DM) interaction. In this work, we show that the inclusion of weak next-nearest-neighbor DM interaction in the frustrated $J_1\text{−}{J}_2$ honeycomb-lattice Heisenberg antiferromagnet leads to the emergence of field-induced incommensurate antiferromagnetic meron-antimeron pairs and antiferromagnetic skyrmion structures. Using the Luttinger-Tisza approximation and large-scale Monte Carlo simulations, we report that, for lower values of $J_2/J_1$, antiferromagnetic meron-antimeron pair crystal and gas phases emerge within a small magnetic field window. In these meron phases, the fundamental unit consists of a meron-antimeron pair residing on different sublattices of the honeycomb lattice, even in the gas phase, where they exhibit greater mobility. For larger $J_2/J_1$, a two-layer-like three-sublattice antiferromagnetic skyrmion crystal phase is stabilized over a wider magnetic field range. At lower temperatures, this region splits into two distinct antiferromagnetic skyrmion phases with skyrmions of different sizes, reflecting the influence of frustration and thermal effects on the stabilization of these topological textures. Interestingly, both meron and skyrmion low-temperature phases connect to spiral spin liquid phases of the honeycomb lattice at higher temperatures. Additionally, we analyze the emergent single-$q$ and double-$q$ phases at low temperatures, constructing a comprehensive phase diagram.