We discuss a possibility of superconductivity in the $p$-wave magnets. These are recently discovered materials that have zero net magnetization by symmetry and finite nonrelativistic spin splitting of electron bands, like in altermagnets. Similarly, the spin polarizations are collinear in the momentum space. Yet, as opposed to altermagnets, the magnetization is noncollinear in the real space, and the spin splitting obeys time-reversal symmetry in the momentum space. As a result, if such material harbors superconductivity (due to phonons or any other mechanism), the only supported superconducting symmetry is Ising superconductivity, an exotic symmetry where any Cooper pair is a 50:50 mix of singlet and triplet. This unusual behavior is also in stark contrast to a regular antiferromagnet, which can support Cooper pairs of any parity, and altermagnets, which can only support nonunitary triplet pairs. The presence of a large triplet component and enhanced resilience against pair breaking is inherent to the $p$-wave magnets and, as such, is unconventional as it does not materialize in conventional spin-orbit-coupling–induced Ising superconductors.

Chromium (Cr) is one of the few transition metals whose body-centered cubic (bcc) structure remains stable over a wide pressure range, but its high-temperature stability and melting behavior at terapascal pressures are still elusive. Here, we use large-scale molecular dynamics simulations based on machine-learning interatomic potentials (MLIPs) to investigate the phase stability and melting of Cr at pressures up to 2 TPa. Gibbs free energies calculation and direct transformation simulations place the bcc-hcp boundary at 1393 GPa at 0 K and in the 1.4–2.0 TPa range at finite temperature. The melting temperature of Cr rises from 2135 K at ambient pressure to $12925\pm 25\mathrm{K}$ at 2 TPa. Above $\sim 50\mathrm{GPa}$ and at temperatures approaching melting, bcc-Cr enters a dynamic regime in which atoms undergo collective jumps while the bcc lattice remains intact, which closely resembles the behaviors that have been reported for other bcc metals, such as Fe under Earth's inner-core conditions and Ti near its ambient-pressure melting point. Finite-temperature phonon calculations reveal pronounced softening of the transverse acoustic branch along the Γ-N direction with increasing temperature, together with the defect-assisted fast diffusion along the $\langle 111\rangle$ direction, provide the microscopic origin of the cooperative displacements. These results identify Cr as a useful high-pressure bcc system for examining the connection between anharmonic lattice dynamics, shear softening, and cooperative atomic transport under extreme compression.

The Mpemba effect, in which a system initially farther from equilibrium relaxes faster than a closer one, has been observed in a wide variety of linear and nonlinear systems. Here we develop a unified framework for the Mpemba effect in many-body systems near equilibrium based on the spectral geometry of the relaxation operator. We distinguish a nonuniform Mpemba effect, associated with a crossing of global distances to equilibrium, from a strict componentwise Mpemba effect, in which the initially hotter state remains larger in every degree of freedom yet relaxes faster. We show that reciprocal systems admit only the former, whereas reciprocity breaking renders the relaxation operator non-normal and can enable the latter. These results identify reciprocity and non-normality as key ingredients governing anomalous relaxation in linear many-body systems.

MnTe has recently attracted exceptional attention due to its well-established altermagnetism, prompting a thorough reexamination of its properties. In particular, it was found that a Raman-active excitation at $\sim 175{\mathrm{cm}}^{-1}$, routinely assigned to the $E_{2g}$ phonon, is incompatible with this interpretation. It was further hypothesized that this mode is a “leakage,” due to symmetry lowering, of an otherwise forbidden phonon. Here, using first-principles calculations, we decisively rule out this hypothesis and propose an alternative interpretation that the “mystery mode” is an electronic excitation, i.e., a plasmon, enabled by hole self-doping. The resolution of this mystery will require additional experiments and could shed new light on the nature of electronic transport in MnTe.

We investigate frustrated magnetism of a corner-connected square-plaquette Heisenberg model with exchange interactions along the edges $\left(J_1\right)$, along interplaquette links $\left(J_2\right)$, and along square diagonals $\left(J_3\right)$. Using Luttinger-Tisza (LT) minimization of the Fourier interaction matrix $\mathcal{J}\left(\mathbf{q}\right)$ together with large-scale Monte Carlo (MC) simulations, we obtain a classical low-temperature magnetic phase diagram in the normalized plane $(J_1/|J_2|,J_3/|J_2\left|\right)$. The two methods play complementary roles: the LT analysis provides the zero-temperature candidate ordering wave vectors, while the MC simulations elucidate the resulting ordering tendencies under the hard-spin constraint at low but finite temperatures. Three regimes emerge at low temperatures: an antiferromagnetic phase, a ferromagnetic phase, and a degenerate spin state with up-up-down-down (uudd) ordering (DS). For the frustrated degenerate spin state, LT exhibits linelike minima along $q_x=\pm q_y$ in the $hk$ plane, revealing a highly degenerate spin configuration that violates the hard-spin constraint. The MC results uncover a state with quasi-two-dimensional ordering. The DS regime is intrinsically multi-$\mathbf{q}$: the ordered texture assembles itself from symmetry-related modes on the lines, producing a “uudd” spin arrangement comprising distinctive strong antiferromagnetic correlations on diagonals, ferromagnetic correlations on corner links, and highly suppressed correlations on the edges. The field-temperature phase diagram for a representative parameter point in the DS regime, determined by MC simulations, yields field-induced distinct regions of negatively and positively correlated layers. These two regions are separated by a curve corresponding to negligible interlayer correlations. Our $\mathrm{LT}+\mathrm{MC}$ framework delivers a well-controlled classical baseline and operational diagnostics for corner-connected frustrated square-plaquette systems, thereby benchmarking future approaches that incorporate quantum-fluctuation effects.

Employing molecular dynamics simulations we observe formation of a complex metastable carbide ${\mathrm{Fe}}_7{\mathrm{C}}_3$ on the surface of ${\mathrm{Fe}}_3$C mediated by a zigzag interface that is almost ideally coherent. We show that formation of dynamic quasiparallel Fe chains and their reconstruction into Fe rings induced by C interstitials are two important atomistic mechanisms underlying the formation of this metastable carbide. Our study elucidates the atomistic mechanism underlying the formation of this specific metastable carbide in the Fe-C system, and suggests that the unveiled role of coherent zigzag interfaces may offer useful perspectives for understanding and inspiring future investigation of metastable phase formation in related systems.

Disordered stealthy hyperuniform materials exhibit the statistical isotropy of a liquid combined with some of the structural properties of a crystal—including homogeneity, suppressed density fluctuations at large length scales, bounded holes, and a structure factor $S\left(k\right)$ that vanishes for a finite range of wave vectors, $0<k\le K$. Numerous studies have shown that this combination leads to highly unusual physical properties for a disordered medium, including optical transparency, effective delocalization, ultrafast spreadability, optimal diffusion coefficients and conductivities, and complete isotropic photonic band gaps. Gyromorphs, point patterns whose structure factor includes rings of intense Bragg-like peaks arranged with discrete $G$-fold rotational symmetry, were recently introduced as counterexamples: disordered media that can somehow achieve the same physical properties, in some cases with higher performance, without stealthiness or hyperuniformity. In this paper, we resolve the puzzle of how gyromorphs fit consistently with the stealthy hyperuniform studies. We first show that gyromorphs are actually hyperuniform and, in the large-$G$ limit where they become nearly isotropic, they belong to the weakest form of hyperuniformity, known as class III. Thus, gyromorphs should have comparatively degraded physical properties compared to stealthy hyperuniform media, which belong to the strongest form of hyperuniformity, known as class I. We verify this expectation using the rigorous spectral Green's-matrix method for the calculation of the density of states and Purcell factors in large arrays of electric dipoles. We find that gyromorphs display size-dependent pseudogaps richly populated by localized states rather than smooth band gaps like those found for highly stealthy hyperuniform (class I) materials or in deterministic structures such as Vogel spirals and triangular lattices. Furthermore, we predict similar disorder-induced degradation relative to stealthy hyperuniformity with regard to transparency, spreadability, and diffusion properties.

The magnetic ground state of ${\mathrm{RuO}}_2$ has been under intense debate. Using first-principles calculations, we show that compressive strain along the [001] direction stabilizes an itinerant magnetism in ${\mathrm{RuO}}_2$ thin films grown on (100) and (110) ${\mathrm{TiO}}_2$ substrates. We further identify that compressive strain enhances the density of states near the Fermi level, resulting in a Fermi surface instability and the emergence of altermagnetism. The magnitude of strain and the associated increase in the density of states can be tuned by varying the film thickness, as systematically confirmed by x-ray diffraction and photoemission spectroscopy measurements. Symmetry analysis further reveals that (100) ${\mathrm{RuO}}_2$ hosts an ideal altermagnetic order, whereas broken symmetry in (110) films leads to a ferrimagnetic state. Finally, we discuss the effects of Hubbard $U$ parameters and evaluate the realistic tunneling magnetoresistance of (100) ${\mathrm{RuO}}_2$.

We report neutron diffraction under applied magnetic fields and complementary zero-field neutron spectroscopy measurements on ${\mathrm{Cs}}_2{\mathrm{RuO}}_4$. Previous work [S. D. Nabi et al., Phys. Rev. B 112, 134436 (2025)] identified a spin-flop-like transition accompanied by a quantum critical point within the ordered phase, attributed to strong frustration between alternating single-ion anisotropy planes. Here, we quantitatively confirm the predicted field evolution of the magnetic structure using neutron diffraction. Furthermore, analysis of the excitation spectrum within an SU(3) spin-wave framework resolves previously undetermined parameters of the minimal spin Hamiltonian and lifts the associated degeneracies.

Binary sesquioxides ($M_2{\mathrm{O}}_3$-type metal oxides) are considered potential candidates for hydrogen permeation barriers (HPBs) under both ambient and high-pressure conditions. However, our previous work revealed that the high-pressure ${\mathrm{Al}}_2{\mathrm{O}}_3$ phase [${\mathrm{Rh}}_2{\mathrm{O}}_3\left(\mathrm{II}\right)$ phase] exhibits ultrahigh hydrogen diffusivities. In this paper, we systematically surveyed the phase transition patterns of the binary sesquioxides and identified ${\mathrm{Er}}_2{\mathrm{O}}_3$ as a superior HPB candidate that exhibits a different phase transition pattern from that of ${\mathrm{Al}}_2{\mathrm{O}}_3$. Since only shared-edge octahedral voids are present in the high-pressure phase of the seven-coordinated erbium-centered polyhedra of ${\mathrm{Er}}_2{\mathrm{O}}_3$, hydrogen atom diffusion occurs across the shared edge between adjacent octahedral voids. This geometric confinement induces a shift from electrostatic to covalent interactions in hydrogen-oxygen covalent interactions during diffusion, thereby increasing the energy barrier; e.g., the diffusion energy barrier of a hydrogen atom in the C-RES phase is 0.50 eV at 0 GPa, and it drastically increases to 1.28 eV in the A-RES phase at 20 GPa. Our findings establish a selection principle for HPBs: choosing crystal phases with highly coordinated cation-centered polyhedra shifts hydrogen-oxygen interaction from electrostatic to covalent during diffusion, strongly suppressing hydrogen diffusion.

Some members of the family of ferroelectric topological crystalline insulators have recently emerged as highly promising materials for fundamental studies in ferronics, spintronics, and orbitronics, as well as for applications because of their Rashba-like spin and orbital splitting in electronic structures and the possibility of voltage-controlled ferroelectric polarization for electrical control of the sign of the spin-orbital charge conversion. In this paper, we report the observation of strong orbital-to-charge conversion in one member of this family, namely SnTe. Ferromagnetic resonance driven spin and orbital pumping (spin-orbital pumping) experiments were performed in heterostructures containing one layer of SnTe with thicknesses varying in the range 3–20 nm and using different ferromagnetic layers to inject the spin and orbital currents (spin-orbital current) into the SnTe layer. The experiments are consistent with orbital-to-charge conversion in SnTe being predominantly governed by the inverse orbital Rashba-Edelstein effect (IOREE). These results suggest that topological surface states play an important role in the orbital-to-charge conversion. From the data for all samples, we obtain a negative IOREE parameter ${\lambda }_{\mathrm{IOREE}}=-29\pm 3.5$ pm, where the negative sign is consistent with a counterclockwise orbital configuration in the surface states. This value is more than one order of magnitude larger than its spin counterpart, consistent with theoretical predictions for a similar member of the family, namely GeTe. Our results corroborate the investigation of IOREE by the injection of spin-orbital currents in a ferroelectric topological crystalline insulator.

Magnetic skyrmions are nanometric swirling spin textures that exhibit remarkable stability at finite temperatures, making them promising candidates for spintronic applications. Achieving controllable stability and transitions between distinct topological structures is crucial for practical implementations. In this work, we investigate the effect of uniaxial mechanical strain on a magnetic model on the kagome lattice, focusing on skyrmion stability and emergent topological phases. To this end, we consider a Heisenberg model that includes exchange interactions and both in-plane and out-of-plane Dzyaloshinskii-Moriya interactions. Using a combination of spin-lattice dynamics and Monte Carlo simulations, we explore uniaxial strain variations in the range of $-10$ to $10\%$, showing important effects on the phase diagram. For compressive strain, we find that the density of skyrmions in the skyrmion gas phase can be tuned and that the stability of this phase extends to higher temperatures. Tensile strain, in contrast, reduces the number of skyrmions and promotes transitions to other magnetic states. Within this regime, strain levels of about $(\sim 4-6\%)$ lead to a change in topological charge, turning skyrmions $(Q=-1)$ into antiskyrmions $(Q=+1)$. We also examine how strain affects other phases commonly appearing in skyrmion-hosting systems, such as the helical and fully polarized states, showing that mechanical deformation alters their stability and characteristic properties. Finally, we compare these results with the strain response of a more conventional skyrmion model, in order to clarify the role of the different interactions involved. Our results identify strain as an experimentally accessible route for engineering topological spin textures.

We report on the synthesis and characterization of an yttrium-containing high-entropy alloy (HEA) superconductor obtained from a nominal YNbTiZrHf composition. Structural analysis reveals a body-centered-cubic matrix with minor yttrium-rich hexagonal precipitates. Comprehensive measurements of electrical resistivity, magnetization, ac magnetic susceptibility, and specific heat confirm bulk type-II superconductivity with a transition temperature $T_{\mathrm{c}}\approx 6.1\mathrm{K}$, a critical current density $J_{\mathrm{c}}\approx 45{\mathrm{kA}/\mathrm{cm}}^2$, and an upper critical field ${\mu }_0{H}_{\mathrm{c}2}=12.5\mathrm{T}$, exceeding the Pauli limit due to strong spin-orbit scattering. The superconducting phase diagram, constructed from $J_{\mathrm{c}}\left(T\right)$, $J_{\mathrm{c}}\left({\mu }_{0}H\right)$, and ${\mu }_{0}H\left(T\right)$ data, is reported for a HEA superconductor. Flux pinning analysis indicates dominant surface pinning with a secondary point contribution, while collective pinning theory reveals a crossover from $\delta T_{\mathrm{c}}$-type to $\delta l$-type pinning with increasing field. The estimated depairing current density $J_{\mathrm{d}}\approx 21\mathrm{MA}/{\mathrm{cm}}^2$, which is more than 2 orders of magnitude higher than the experimental $J_{\mathrm{c}}$, suggests significant potential for performance enhancement through microstructural optimization.

${\mathrm{Re}}_{0.6}{\left(\mathrm{HfZrNbTi}\right)}_{0.4}$ is a hexagonal high-entropy alloy superconductor that serves as a model system for exploring the interplay of disorder, crystal structure, and superconductivity. We investigate its superconducting properties under pressures up to 56.6 GPa using electrical transport measurements. The superconducting transition temperature, $T_c$, exhibits a modest increase at low pressures in the hexagonal phase, likely associated with pressure-induced changes in the electronic structure and electron-phonon coupling, and then saturates as it approaches the previously reported hexagonal-to-bcc structural transition. Despite the associated volume collapse, $T_c$ evolves smoothly across the transition region, likely reflecting the broad coexistence of the hexagonal and bcc phases over the transition pressure interval. Upon decompression, $T_c$ is systematically lower than during compression, consistent with hysteresis of the structural transition and metastable retention of the high-pressure phase. The upper critical field, $H_{c2}\left(0\right)$, exhibits a weak nonmonotonic pressure dependence and remains well below the Pauli paramagnetic limit, consistent with conventional spin-singlet pairing. These results demonstrate that superconductivity in ${\mathrm{Re}}_{0.6}{\left(\mathrm{HfZrNbTi}\right)}_{0.4}$ remains remarkably robust against both lattice compression and structural transformation, consistent with the disorder-averaged superconducting state proposed for high-entropy alloys.

We compute the particle–hole bubble for an Ising-nematic metal when the critical Fermi surface approaches the Brillouin zone boundary for $d=2$ dimensions. We find two qualitatively distinct contributions: (i) the standard antipodal piece, which gives ${\mathrm{\Pi }}_{\mathrm{ATP}}(\mathbf{q},i\mathrm{\Omega })\propto \mathrm{\Omega }/q$, and (ii) an additional umklapp piece from electrons near the zone boundary, which gives ${\mathrm{\Pi }}_{\mathrm{U}}(\mathbf{q},i\mathrm{\Omega })\propto {\mathrm{\Omega }}^{\alpha }$ at the minimum umklapp momentum $q\approx {\mathrm{\Delta }}_q$, with $\alpha =2/3$ or $1/2$ depending on the temperature $T$. At high $T$ when $\alpha =1/2$, the minimum $T$ for the activation of linear/quasilinear in $T$ resistivity, which is expected to be $T_U\propto {\mathrm{\Delta }}_q^3$ from $z=3$ criticality, could potentially get reduced to $T_U\propto {\mathrm{\Delta }}_q^4$ due to the $\sqrt{\mathrm{\Omega }}$ term. We discuss why due to fermion self-energy effects, we find only one hyperspecific scenario where this possibility might be realized and offer some evidence for the reduction of $T_U$ at the level of a scattering rate estimate for this case. For $d=3$ the umklapp contribution gives ${\mathrm{\Pi }}_{\mathrm{U}}\sim \mathrm{\Omega }$ irrespective of $T$; therefore $T_U$ is not modified in this case.

We have performed density functional theory (DFT) calculations to characterize the energetics, and the atomic and electronic structure, of stacking faults in GaN, both in the stable hexagonal wurtzite (wz) phase and in the metastable cubic zincblende (zb) phase. In wz GaN, SFs on the $\left\{0001\right\}$ planes can be divided into three different intrinsic stacking faults (${\mathrm{I}}_1, {\mathrm{I}}_2$, and ${\mathrm{I}}_3$) and one extrinsic stacking fault (E). Based on the calculated formation energy, ${\mathrm{I}}_1$ is the most stable SF of wz GaN in agreement with experiment. In zb GaN, SFs form on $\left\{111\right\}$ planes, giving one type each of intrinsic, extrinsic, and twin SFs. In our calculations, the three types of SFs have similar formation energy. To characterize the effect of the stacking faults on the electronic structure of the material, we examined the band density. We found that the bands near the valence band maximum in wz GaN are localized on the Ga-polar side of the stacking fault (i.e., on the Ga side of the Ga-N bonds perpendicular to the SF), with the bands near the conduction band minimum more on the N-polar side, though somewhat delocalized. We found the opposite trend in zb GaN; this behavior is caused by a redistribution of charge near the interface. We also show the band offsets for the stacking faults, finding that they are very sensitive to local conditions, but can all be described as type II interfaces, with the presence of a stacking fault reducing the gap locally in both wz and zb.

We develop an interpretable, data-driven framework to quantify how single-particle band geometry governs the stability of fractional Chern insulators (FCIs). Using large-scale exact diagonalization, we evaluate an FCI metric that yields a continuous spectral measure of FCI stability across parameter space. We then train Kolmogorov-Arnold networks (KANs)—a recently developed interpretable neural architecture—to regress this metric from two band-geometric descriptors: the trace violation $T$ and the Berry curvature fluctuations ${\sigma }_B$. Applied to spinless fermions at filling $\nu =1/3$ in models on the checkerboard and kagome lattices, our approach yields compact analytical formulas that predict FCI stability with over $>80\%$ accuracy in both regression and classification tasks, and remain reliable even in data-scarce regimes. The learned relations reveal model-dependent trends, clarifying the limits of Landau-level-mimicking heuristics. Our framework provides a general method for extracting simple, phenomenological “laws” that connect many-body phase stability to chosen physical descriptors, enabling rapid hypothesis formation and targeted design of quantum phases.

Shallow nitrogen-vacancy (NV) centers in diamond are useful for near-surface sensing, but the negatively charged state ${\mathrm{NV}}^{-}$ is often difficult to stabilize close to the surface. Here we study the depth dependence of NV formation and charge-state stability in nitrogen-implanted diamond using spatially resolved photoluminescence (PL) spectroscopy, dynamic secondary ion mass spectrometry (D-SIMS), stopping and range of ions in matter (SRIM) simulations, and first-principles density functional theory (DFT) calculations. Although the near-surface region contains a higher nitrogen concentration, its NV-related PL emission is much weaker than that from the shallow subsurface region. This behavior shows that nitrogen incorporation alone is not sufficient to explain the observed ${\mathrm{NV}}^{-}$ stability. The depth profiles obtained from D-SIMS and SRIM support the intended difference between the near-surface and shallow-subsurface implantation regions. To examine the possible role of residual implantation damage, we further compare ideal NV and carbon-interstitial-related NV (NV-int) defect models by DFT. The interstitial-related defect model gives an upward shift of the $\varepsilon \left(0/-\right)$ transition level by about 3.23 eV. Charge-density-difference and density-of-states analyses further reveal local charge redistribution and reconstruction of defect-related electronic states around the NV center. These changes establish a microscopic explanation for the reduced stability of ${\mathrm{NV}}^{-}$ in defect-rich near-surface regions. Our results indicate that shallow NV engineering should focus not only on nitrogen placement, but also on reducing residual implantation-induced defects.

The three-dimensional (3D) magnet ${\mathrm{KBaFe}}_2$(${\mathrm{PO}}_4{)}_3$ hosts an effective tetratrillium spin lattice of ${\mathrm{Fe}}^{3+}$ ($S=5\text{/}2$) ions, offering a prototypical platform to study frustration-driven phenomena in 3D. Through magnetization, specific heat, ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR), and muon spin relaxation ($\mu \mathrm{SR}$) experiments, supported by first-principles calculations, we uncover an unconventional ground state. Despite strong antiferromagnetic interactions with a large Curie-Weiss temperature ${\theta }_{\mathrm{CW}}=-70\left(2\right)\mathrm{K}$, no magnetic long-range order is observed down to 30 mK. Below $T^{*}\simeq 3.5\mathrm{K}$, the NMR linewidth becomes nearly field independent and the spin-spin relaxation rate $1/T_2$ saturates, accompanied by a two-component relaxation in the transverse nuclear magnetization $M_{xy}$. The latter indicates the emergence of short-range dynamical correlations, which was further corroborated by a robust and field-insensitive broad maximum in specific heat. In $\mu \mathrm{SR}$, we detect neither a static internal field nor spin freezing; instead, the spins remain dynamic down to 30 mK and the asymmetry curves are best described by two coexisting dynamic relaxation channels: a dominant fast (sporadic) channel and a slower Markovian component. Their differing weights and fluctuation rates suggest microscopic inhomogeneity in spin dynamics. These persistent low-temperature spin fluctuations are found to be intrinsic to the 3D frustrated tetratrillium geometry, exemplifying ${\mathrm{KBaFe}}_2$(${\mathrm{PO}}_4{)}_3$, a rare 3D antiferromagnet with a classical spin that fosters unconventional dynamics.

A periodically driven Fermi gas coupled to a simple boson bath reaches a nonequilibrium steady-state occupation with sharp nonanalyticities at certain momenta. Here, we demonstrate that these nonanalyticities behave as emergent Fermi surfaces by showing that they give rise to quantum oscillations of observables with a period controlled by the effective Fermi-surface area enclosed by these nonanalyticities. However, these oscillations have several striking differences with standard equilibrium quantum oscillations. For example, they remain nonanalytic at finite temperatures, their amplitude can survive up to extremely high temperatures comparable to the frequency of the drive, and they can display nonmonotonic temperature dependence completely at odds with standard Lifshitz-Kosevich behavior.