We show strong coupling between antiferromagnetic magnons and microwave cavity photons at both high and externally controllable magnon frequencies. Using the fully quantum mechanical path-integral method, we study an antiferromagnetic (AFM) insulator interfaced with a topological insulator (TI), taking ${\mathrm{Bi}}_2{\mathrm{Se}}_3\text{−}\mathrm{MnSe}$ as a representative example. We show that the mutual coupling of the spin-polarized surface states of the TI to both the squeezed magnons and the circularly polarized cavity photons results in a Chern-Simons term that activates the stronger electric, rather than magnetic, dipole coupling. Moreover, a squeezing-mediated enhancement of the coupling is achieved due to the unequal interfacial exchange coupling to the AFM sublattices, resulting in a coupling strength up to several orders stronger than for direct magnon-photon coupling. While direct cavity-AFM coupling has so far been limited in its applicability due to weak or low frequency coupling, this result may advance the utilization of high-frequency cavity magnonics and enable its incorporation into quantum information technology.

High-entropy compounds, where multiple elements occupy a single crystallographic site in a highly disordered manner, challenge conventional understandings of electronic structures based on periodicity and well-defined band dispersion. Here, we report a detailed nuclear magnetic resonance study of the high-entropy superconductor $X_{0.6}{\mathrm{Pt}}_{0.4}\mathrm{Sb}$ ($X$ = Ru, Rh, Pd, Ir), revealing a spatially homogeneous electronic environment in the normal state, in stark contrast to its crystallographically disordered lattice. The superconducting state exhibits a small but solid Hebel-Slichter coherence peak followed by a significant decrease in the nuclear spin-lattice relaxation rate, providing compelling evidence for fully gapped $s$-wave pairing. Our findings not only deepen the understanding of superconductivity in highly disordered quantum materials but also open an alternative pathway for exploring superconducting states in entropy-stabilized systems.

Exceptional points (EPs) are prominent non-Hermitian band degeneracies that give rise to a variety of intriguing and unconventional phenomena. Similar to Weyl and Dirac points, EPs carry topological charges and comply with the celebrated fermion doubling theorems in lattices. Beyond these characteristics, EPs exhibit more exotic topological properties, particularly non-Abelian braiding topologies not seen in conventional degeneracies. However, these core concepts of EPs have been established under the assumption of toroidal Brillouin zones. Here, we investigate EPs in two-dimensional non-Hermitian lattices where the fundamental domain of the Brillouin zone is a Klein bottle, rather than a torus assumed in previous studies. We find that EPs do not necessarily appear in pairs with opposite topological charges in the Brillouin Klein bottle, thus violating the fermion doubling theorem. The violation occurs because, without crossing the boundary, the sum of the topological charges of EPs is in fact an even number rather than zero. Moreover, we uncover unique braiding topologies of EPs that cannot be captured by existing theories. Specifically, the composite braidings around all EPs equals the braiding along the boundary of the Brillouin Klein bottle. This braiding topology further confirms the failure of the fermion doubling theorem and allows us to explore the non-Abelian braidings of EPs beyond the scope of topological charges. Our work highlights the fundamental role of Brillouin-zone topology in non-Hermitian systems.

The behavior of charge carriers in polar materials is governed by electron-phonon interactions, which affect their mobilities via phonon scattering and may localize carriers into self-induced deformation fields, forming self-trapped polarons. We present a first-principles study of self-trapped polaron formation in paradigmatic polar semiconductors and insulators using the variational polaron equations framework and self-consistent gradient optimization. Our method incorporates long-range corrections to the electron-phonon interaction, essential for finite-size systems. We demonstrate how the variational approach enables the identification of multiple polaronic states and supports the analysis of polarons with arbitrarily large spatial extent via energy filtering. The potential-energy surfaces of the resulting polarons exhibit multiple local minima, reflecting distinct, symmetry-broken polaronic configurations in systems with degenerate band edges. Our findings align with previous theoretical studies and establish a robust foundation for future ab initio studies of polarons, especially those employing variational methods.

Phase change material (PCM) based information memory mainly relies on the rapid transition from amorphous and crystalline states of these systems. While extensive research has been focused on the crystallization process of PCM, physical mechanisms on the amorphization process have been limited and insufficiently explored to date. Here, we systematically investigate the amorphization dynamics and local order of tantalum (Ta) -doped ${\mathrm{Sb}}_2\mathrm{Te}$ material under thermally induced melting-quenching and photoexcitation processes, using ab initio molecular dynamics and real-time time-dependent density-functional theory methods, respectively. During the melt-quenching process, the doping of Ta atoms enhances local order by promoting the formation of high-coordination and triangular configurations, thereby improving the thermal stability of the amorphous structure. The core mechanism of the pulsed laser-induced amorphization originates from the dynamic modulation of interatomic bonding characteristics by photoexcited carriers, which can reduce the amorphization barrier and drive structural instability. Compared with the former, the latter induces the increase of tetrahedral structure and a higher number of rings in the amorphous process, while the local Peierls distortion attenuates, reducing the risk of resistance drift. This work provides insights on the amorphization dynamics of Ta-doped ${\mathrm{Sb}}_2\mathrm{Te}$ and related PCM induced by both thermal and photoexcitation.

Sapphire $\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$, known for its remarkable incompressibility at ambient conditions, plays a pivotal role in both static and dynamic compression research. Accurately characterizing its equation of state (EoS) is essential for these applications. We present a complete Hugoniot of ${\mathrm{Al}}_2{\mathrm{O}}_3$ as locus of experimentally assessed, high-precision, pressure, density and temperature states up to 14 Mbar and 43 kK. The Hugoniot is established with single shock experiments using magnetically launched hyper velocity flyers on the Z Accelerator at Sandia National Laboratories. We explore principal Hugoniot states at very high shock $T$ and $p$ in the solid phase, tracking the solid-liquid boundary and culminating at 2.4-fold compression, where data provides a direct constraint on the liquid phase. Corresponding shock release data probe thermodynamic states complementary to the Hugoniot and place additional constraints on tabular EoS models. Our findings indicate a significant deviation from existing tabular EoS models for ${\mathrm{Al}}_2{\mathrm{O}}_3$ dictating a comprehensive overhaul. We develop two advanced EoSs for ${\mathrm{Al}}_2{\mathrm{O}}_3$ the SESAME 97412 model, featuring an extensive phase diagram that includes three solid phases and the liquid phase, and the updated LEOS 2200m2 model. EoS development is assisted with Quantum Molecular Dynamics simulations. Our experimental data allows for stringent testing of our EoSs. Both models accurately capture the Hugoniot of ${\mathrm{Al}}_2{\mathrm{O}}_3$ up to the highest pressures and temperatures. Rigorous experimental determination of extreme pressures and temperatures, paired with sophisticated models, advances the frontier of EoS development beyond 1 terapascal.

Polar ${\mathrm{VOSe}}_2{\mathrm{O}}_5$, belonging to the $P4cc$ space group ($C_{4V}$ symmetry), was recently discovered to host a rare Néel-type skyrmion phase within a very narrow range of temperature and magnetic field. Motivated by this discovery, we investigated the effect of pressure on its magnetic properties, focusing on improving the stability of the skyrmion phase. At ambient pressure, two magnetic transitions were observed at $T_{\mathrm{C}1}\sim 7.4\mathrm{K}$ and $T_{\mathrm{C}2}\sim 4.0\mathrm{K}$. Notably, the contrasting behavior of these transitions under applied magnetic fields—$T_{\mathrm{C}1}$ increases, whereas $T_{\mathrm{C}2}$ is suppressed—reflects the magnetic anisotropy in ${\mathrm{VOSe}}_2{\mathrm{O}}_5$. Neutron diffraction refinements revealed a three-up-one-down ferrimagnetic configuration aligned along the $b$ axis at 1.8 K, and an incommensurate cycloidal spin structure rotating within the $bc$ plane at 6 K, further demonstrating the intrinsic magnetic anisotropic in ${\mathrm{VOSe}}_2{\mathrm{O}}_5$. Pressure-dependent ac susceptibility measurements showed $T_{\mathrm{C}1}$ increasing by 0.043(3) K/kbar and $T_{\mathrm{C}2}$ decreasing by −0.052(4) K/kbar, indicating pressure-tunable anisotropy. The field-temperature (H-T) phase diagram confirms the stabilization of the Néel-type skyrmion phase under 14.21 kbar of pressure, with its area expanding approximately threefold. These findings underscore the role of pressure in promoting Néel-type skyrmion stability through modulation of the magnetic anisotropy, offering valuable insights into tuning topological phases for spintronics and related technological applications.

We present a general representation for solving problems in many-body perturbation theory. By projecting the single-particle Green's function to an auxiliary space, we show how one can convert an arbitrary Feynman graph to a universal kernel representation. Once constructed, the computation kernel contains no problem-specific information yet contains all explicit temperature and frequency dependence of the diagram. This computation kernel is problem agnostic, and valid for any physical problem that would normally leverage the Matsubara formalism of many-body perturbation theory. The result of any diagram can be written as a linear combination of these computation kernel elements with coefficients given by a sum over products of known tensor elements that are themselves problem-specific and represent spatial degrees of freedom. We probe the efficacy of this approach by generating the computation kernel for a low-order self-energy diagram, which we then use to construct solutions to distinct problems.

The optical control of spin- and valley-selective gapless states in two-dimensional materials presents new opportunities for next-generation spintronic and valleytronic technologies. In this work, we study monolayer jacutingaite (${\mathrm{Pt}}_2{\mathrm{HgSe}}_3$), a quantum spin Hall insulator with strong intrinsic spin-orbit coupling, under irradiation by circularly polarized light. The light-induced Floquet engineering gives rise to tunable topological phases, including transitions to spin- and valley-polarized semimetallic states. We probe the topological transitions using spin and orbital Edelstein effects—nonequilibrium responses from spin-orbit coupling in noncentrosymmetric systems. While not a full substitute for Chern invariants, sharp changes in these responses, such as a discontinuity in spin Edelstein conductivity and vanishing orbital susceptibility, signal the onset of the semimetallic regime. Furthermore, we investigate how the growth and suppression of the spin Edelstein responses across the topological phase transition depend on the interband scattering time. These findings establish the Edelstein effect as a sensitive and experimentally accessible probe of light-induced topological transitions in quantum materials.

Weyl semimetals are prospective topological materials, in which conduction and valence bands touch each other in a discrete number of points. This opens up prominent electronic properties of Weyl semimetals and noticeably influences light-matter interaction. In this work, we study the light scattering by a spherical particle with a radially oriented gyrotropy axis inspired by the Weyl semimetal response. Using the operator scattering theory, we represent the transfer matrix of the gyrotropic spherical layer as a product of matrix exponentials, which allows us to calculate the wavelength-dependent scattering efficiency and analyze the multipole structure of the observed resonances. We demonstrate the change of the scattering pattern upon polarization ellipse deformation for considered Weyl semimetal scatterers and reveal the scattering peculiarities of multilayer Weyl semimetal particles with alternating orientation of the gyrotropy axis. In this research, we pave the way for designing polarization-sensitive nanophotonic devices.

We have investigated the evolution of the atomic and electronic structure of Sn deposited on the Ag(001) surface using low-energy electron diffraction (LEED), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations. We find that, for all Sn coverages $x$ up to 1 ML, the thermodynamically favoured configurations correspond to the formation of a bimetallic Sn-Ag substitutional surface alloy in the topmost layer. The LEED data reveal distinct superstructures for varying Sn coverages. We find that the effective sizes of Sn atoms on the Ag(001) surface are significantly larger than those of surface or bulk Ag atoms. As a result, the formation of the substitutional surface alloy relieves tensile stress at the surface. The theoretically computed “unfolded” band structure agrees excellently with ARPES data. Surprisingly, this is true even in cases where experiments and calculations suggest different atomic structures. Our findings suggest that the significant features in the band structure are predominantly influenced by the surface potential, which is less sensitive to the precise details of the atomic structure, but rather to the average surface composition.

Fractionalization remains one of the most fascinating manifestations of strong interactions in quantum many-body systems. In quantum magnetism, the existence of spinons—collective magnetic excitations that behave as quasiparticles with fractional quantum numbers—is proven in spin chains, but the criteria for their appearance in higher dimensions remain disputed. Motivated by experiments reporting the observation of spinons at high energies in the square-lattice Heisenberg antiferromagnet, we adopt the approach of extrapolating from where spinons are well defined. We study the dynamical properties of a Gutzwiller-projected wave function, the staggered-flux state, on a rectangular spin-1/2 Heisenberg lattice as a function of the spatial coupling ratio, $\gamma =J_y/J_x$. By studying the spectrum and the spinon separation distribution we show how, as the system evolves from one-dimensional (1D) towards 2D, the spinons become progressively more confined over most of reciprocal space, but remain deconfined at specific wave vectors.

We study the transverse-field Ising model on a square lattice with bond and site dilution at zero temperature by stochastic series expansion quantum Monte Carlo simulations. Tuning the transverse field $h$ and the dilution $p$, the quantum phase diagram of both models is explored. Both quantum phase diagrams show long-range order for small $h$ and small $p$. The ordered phase of each is separated from the disordered (quantum) Griffiths phase by second-order phase transitions on two critical lines touching at a multicritical point. Using Binder ratios we locate quantum critical points with high accuracy. The order-parameter critical exponent $\beta$ and the average correlation-length exponent ${\nu }_{\mathrm{av}}$ are determined along the critical lines and at the multicritical points via finite-size scaling. We find three internally consistent sets of critical exponents and compare them with potentially connected universality classes. The quantum Griffiths phase in the vicinity of the phase transition lines is analyzed through the local susceptibility. Our results indicate that activated scaling occurs not only at the percolation transition, but also at the phase transition line for $p$ smaller than the percolation threshold $p_c$.

The flow of time moves in one direction in any spatial position and orientation in this universe. Chiral objects, which lack mirror symmetry, retain their chirality regardless of their position or orientation. Despite being seemingly independent, time and chirality share common features such as universality—applying to any position and orientation—and a binary nature, such as forward/backward time flow versus left/right chirality. We introduce the concept of time chirality and discuss the conjugate relationship between time chirality and traditional chirality. We explore how time chirality can manifest in certain magnetic states, and examine the physical phenomena associated with time-chiral magnetic states. This discussion offers a fresh perspective on true time-reversal symmetry breaking and temporal nonreciprocity.

We investigate a variant of spin ice whose degenerate ground states are densely packed monopole configurations. An applied field drives this model through a ${\mathbb{Z}}_2$ confinement transition. This phase change is a variant of the U(1) Kasteleyn transition, but instead of saturated order the system has fluctuations in the confined phase, and shows critical scaling on both sides of the transition. Remarkably, the magnetic response scales with the critical exponent of the specific heat in the 3D Ising universality class. We prove this universality using a Kramers–Wannier duality to map to an Ising model. The dual order parameter maps back to a nonlocal string order parameter in the original model, invisible to any local probe. Further, we describe the transition in terms of a bosonic field theory including a pairing term.

Using the valley degree of freedom as a carrier of information for storage and processing, valley polarization plays a crucial role. A variety of mechanisms for valley polarization have been proposed, among which the valley-layer coupling mechanism involves the induction of valley polarization by an out-of-plane electric field. Here, through first-principles calculations, it is found that the weak valley-layer coupling can exist in centrosymmetric $1T\text{−}{\mathrm{FeCl}}_2$ monolayer. It is crucial to note that valley-layer coupling only occurs with out-of-plane magnetization and vanishes with in-plane magnetization. Compared to monolayers with strong valley-layer coupling, ${\mathrm{FeCl}}_2$ requires an extremely strong electric field to achieve the same magnitude of valley splitting. Valley polarization switching can be achieved by manipulating the directions of magnetization and electric field. Reversing only one of these directions switches the valley polarization, whereas reversing both simultaneously leaves it unchanged. Moreover, the simply stacked bilayer ${\mathrm{FeCl}}_2$, as a $PT$-antiferromagnet, can spontaneously achieve valley polarization without an external electric field, highlighting its potential for miniaturization, ultradensity, and ultrafast performance. Our work provides guidelines for identifying materials with weak valley-layer coupling, and further enables the regulation of valley polarization through electric field and stacking engineering.

Scattering of electron in the field of a narrow solenoid with alternating current is considered. Using the eikonal approximation, the wave function of electron, the differential and total scattering cross sections are found. Unlike the case of direct current, the total cross section in the case of alternating current turns out to be finite. An oscillating asymmetry in the differential scattering cross section is discovered. The possibility of experimental observation of the effect is discussed.