We have conducted experiments on potassium chloride grains under temperature, pressure, and irradiation conditions comparable to planetary and astrophysical environments. These experiments are particularly relevant to the investigation of ocean worlds covered with ice shells that may contain ocean-derived salts and which may be exposed to surface irradiation. Irradiation of sylvite (KCl) under cryogenic conditions yields trapped electrons in F- and $M$-center anion vacancies (553 nm and 819 nm, respectively), whereas room temperature measurements after irradiation show additional color-center formation ($R1$ [675 nm], $R2$ [734 nm], and $N$ [978 nm]). We attribute these additional features to the merging of $F$ centers at higher temperatures, yielding colloids. Potassium chlorate (${\mathrm{KClO}}_3$) is identified as a possible radiolytic product resulting from modification of KCl with surficial adsorbed ${\mathrm{H}}_2\mathrm{O}$.

Due to its critical role in magnetization dynamics, Gilbert damping in ferromagnet/nonmagnet multilayer systems has been widely studied. This paper investigates the Gilbert damping of V/Fe/Pt/MgO and V/Pt/Fe/MgO systems using the time-resolved magneto-optical Kerr effect to study the stacking order dependence, that is, the difference between Fe/Pt and Pt/Fe. Significant effective Gilbert damping differences were observed between the Fe/Pt and Pt/Fe systems, with intrinsic Gilbert damping playing a dominant role. As the Fe thickness increases, difference in damping between the two stacking orders decreases. We attribute this difference in stacking orders to varying degrees of interfacial alloying at the Fe/Pt and Pt/Fe interfaces.

Spin arrays provide a framework for studying cooperative spin phenomena and correlated states. Advances in high-frequency electron paramagnetic resonance (HFEPR) above 90 GHz offer new opportunities to investigate these systems, determine the effect of weak spin-spin interactions, and evaluate their magnitudes. Here, we investigate the cupric coordination compound Cu($L-{\mathrm{met})}_2$, where anisotropic $S=\frac{1}{2}$ spins occupy two rotated structural sites, forming weakly coupled spin arrays via supramolecular interactions. Previous EPR studies at 9.7 GHz and 33.6 GHz identified pseudo-one-dimensional magnetic behavior with a single, orientation-independent spectral peak, allowing estimates of exchange couplings. In this work, HFEPR spectra up to 450 GHz and magnetic fields (${\mathit{B}}_0$) up to 16 T display a more complex spectral landscape: the number of resonances switches between one and two as a function of the orientation of ${\mathit{B}}_0$, revealing different dynamical regimes. This behavior indicates a crossover between a collective quantum-correlated phase and a regime where spins behave independently, allowing us to construct quantum dynamical phase diagrams across frequency and field space. These findings reinforce molecular compounds as promising platforms for exploring tunable spin dynamics, with implications for quantum information science. The observation of spin-spin interactions persisting at room temperature highlights their potential for robust quantum coherence in molecular systems.

The spin Nernst effect, an antisymmetric response of a spin current to a temperature gradient, has attracted attention as a spin transport phenomenon arising from the topologically nontrivial band structure of carriers. This effect can occur not only in itinerant electron systems, but also in localized electron systems that emerge due to electronic correlations. In such systems, elementary excitations behaving as bosons govern spin transport, and magnetic interactions originating from spin-orbit coupling can induce a topologically nontrivial band structure. However, such magnetic interactions can potentially break spin conservation, thereby preventing conventional spin currents from being conserved. In this study, starting from a general localized electron model, we formulate the spin Nernst effect in terms of a conserved spin current that remains applicable even in spin-nonconserving systems. To address the torque term appearing in the conserved spin current, we adopt semiclassical theory and derive an expression for the spin Nernst coefficient for bosonic systems. This coefficient consists of two terms originating from the Berry curvature and the quantum metric, which are distinctly different from the spin Berry curvature obtained in an approach that neglects the torque term. We apply our framework to two specific quantum spin models, the Kitaev-Heisenberg and Shastry-Sutherland models, and calculate the temperature dependence of the spin Nernst coefficient. We find that this quantity significantly differs from that obtained by neglecting the torque term in both models. Furthermore, we clarify that the impact of the torque term on the spin Nernst effect strongly depends on the model parameters, suggesting that our formulation based on the conserved spin current is essential for understanding this effect in insulating magnets.

Motivated by the recently discovered bilayer nickelate superconductor, the pressurized ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, we present a renormalized mean-field theory of a bilayer single-orbital $t\text{−}J$ model, highlighting the interplay between magnetism and superconductivity. We analyze the pairing symmetry and magnetic properties of the system, predicting two distinct states in which magnetism and superconductivity coexist. As hole doping increases, the magnetic order is rapidly suppressed. The interlayer hopping $t_{\perp }$ and coupling $J_{\perp }$ promote a transition from intralayer $d$-wave pairing to $s$-wave pairing, which is accompanied by a shift from antiferromagnetic order to a double spin stripe configuration. The latter has been extensively observed in ambient and high-pressure experiments. Our study offers theoretical insights into the coexistence of spin density waves and superconductivity.

The schematic model of interacting spins is introduced, which combines the symmetry of hypercube with the simplicity of random regular graph with degree three, i.e., the random cubic graph. We study the localization transition in this model, which shares essential characteristics with the systems exhibiting many-body localization. Namely, we investigate the transition in terms of the entanglement entropy and entanglement spectrum. We also show that the most significant indicator of the localization transition is the failure of eigenstate thermalization hypothesis, when the distribution of matrix elements of local operators changes from Gaussian to bimodal. It also provides a good estimate for the critical disorder strength.

Extracting useful information from noisy near-term quantum simulations requires error mitigation strategies. A broad class of these strategies rely on precise characterization of the noise source. We study the robustness of probabilistic error cancellation and tensor network error mitigation when the noise is imperfectly characterized. We adapt an Imry-Ma argument to predict the existence of a threshold in the robustness of these error mitigation methods for random spatially local circuits in spatial dimensions $D\ge 2$: noise characterization disorder below the threshold rate allows for error mitigation up to times that scale with the number of qubits. For one-dimensional circuits, by contrast, mitigation fails at an $\mathcal{O}\left(1\right)$ time for any imperfection in the characterization of disorder. As a result, error mitigation is only a practical method for sufficiently well-characterized noise. We discuss further implications for tests of quantum computational advantage, fault-tolerant probes of measurement-induced phase transitions, and quantum algorithms in near-term devices.

The mean-state dynamics of free fermions subject to random projective measurements of local occupation number operators is governed by a Lindblad equation with dephasing noise. In the continuum limit, the equation of motion for the correlation matrix is mapped to a kinetic equation for the Wigner function, which corresponds to a special case of the Bhatnagar-Gross-Krook (BGK) equation without energy conservation. Our main result is the solution to the kinetic equation, showing that the Wigner dynamics emerges from stochastic sampling of classical run-and-tumble processes. As an application, we recover the crossover between ballistic and diffusive transport regimes.

We report on the dynamics of a conducting domain wall under applied dc and ac voltages. These dynamics are modeled for a thin film that hosts an ideal charged domain wall via a combination of time-dependent Ginzburg-Landau equations for the polarization, the Schrödinger equation for the electron gas, and Poisson's equation for the electrostatic potential. The electron dynamics are treated within a Born-Oppenheimer approximation. We find that the electron gas introduces an additional degree of freedom, beyond polarization relaxation, that modifies the dynamical response of the domain wall. While marginally relevant for the dc response, the electron dynamics have a pronounced effect on the film's ac dielectric function. The dielectric function has an intrinsic contribution, due to the bulk susceptibility of the film, and an extrinsic contribution due to the domain-wall displacement. The electron gas affects the dielectric function by changing both the amplitude and phase of the displacement.

Ferromagnetic (FM) Kondo-lattice (KL) compounds often exhibit intriguing magnetic behavior driven by strong crystal electric field (CEF) anisotropy and exchange interactions. Recent studies suggest that many Ce- and Yb-based KL ferromagnets order along the hard-axis or hard-plane determined by their CEF ground state. We performed a survey of Ce-based FM compounds, complemented with new single-crystal synthesis, magnetization measurements, and analysis of the CEF scheme. Our results reveal that hard-axis or hard-plane ordering is less common than previously reported, with most compounds ordering along their easy-axis or easy-plane. We also find no clear correlation between the strength of the Kondo effect and whether a compound adopts hard-axis or hard-plane or easy-axis or easy-plane ordering. Instead, the key driver appears to be the competition between CEF anisotropy and exchange interaction anisotropy. A direct comparison of CeCuSi and ${\mathrm{CeAgSb}}_2$ further indicates that antiferromagnetic interactions along the CEF easy-axis can be crucial in stabilizing the hard-axis FM ordering observed in ${\mathrm{CeAgSb}}_2$. Finally, our results suggest that an anisotropic Ruderman–Kittel–Kasuya–Yosida model could offer deeper insights into the complicated magnetic properties of Ce-based and other heavy-fermion systems.

Recent neutron-diffraction work on the perovskite ${\mathrm{LaMnO}}_3$ has revealed that the Néel temperature increases under high pressure and reaches a maximum at P∼12 GPa. Given the uncertainty in structural determinations from experiment, the origin of this phase transition remains elusive. We simulated the evolution of crystal structure as a function of pressure based on density-functional theory with the exchange-correlation functional at the levels of both standard Perdew-Burke-Ernzerhof and hybrid functional approximations. We confirm a previously postulated phase transition from the orthorhombic phase to the rhombohedral phase at P∼12 GPa by calculating the enthalpy of both structures. Our simulations also demonstrate that the orbital ordering and the orbital mixing as extracted from the local structural distortion are progressively suppressed under high pressure in the orthorhombic phase, which matches the results of neutron diffraction. In addition, our calculations have been extended to simulate the general pressure effect on the structure in orthorhombic $A^{3+}{B}^{3+}{\mathrm{O}}_3$ perovskites. Orthorhombic distortion in the perovskites is described by the difference in lattice parameters b-a. Our simulations reproduce well the contrasting pressure effect on the orthorhombic distortion in different perovskites, i.e., reduced b-a under pressure for perovskites having initially smaller b-a (like ${\mathrm{LaMnO}}_3$, ${\mathrm{LaGaO}}_3$) and increased b-a under pressure for perovskites having larger b-a (like ${\mathrm{LuMnO}}_3$, ${\mathrm{LuGaO}}_3$). Local structural changes revealed from the simulation, which yet remain to be confirmed by experiment, provide an important clue to the origin of these opposite pressure effects exerted on the same type of crystal structure.

The current-induced spin-orbit torque-based devices for magnetization switching commonly relied on the $4d$ and $5d$ heavy metals owing to their strong spin-orbit coupling (SOC) to produce large spin current via spin Hall effect (SHE). Here we present the sizable SHE in CrN, a light-element-based system, and demonstrate the current-induced magnetization switching in the adjacent ferromagnetic layer ${\left[\mathrm{Co}\right(0.35\mathrm{nm}\left)\text{/}\mathrm{Pt}\right(0.3\mathrm{nm}\left)\right]}_3$, which exhibits perpendicular magnetic anisotropy. We found the switching current density of $2.6\mathrm{MA}\text{/}{\mathrm{cm}}^2$. The first principles calculation gives the spin Hall conductivity (SHC) $\sim 120\left(\frac{\hslash }{e}\right)\mathrm{S}\text{/}\mathrm{cm}$ due to intrinsic spin Berry curvature arising from SOC induced band splitting near Fermi energy. The theoretically calculated intrinsic SHC is close to the experimental SHC extracted from second harmonic Hall measurement. We estimated spin Hall angle (${\theta }_{SH}$) $\sim 0.09$, demonstrating efficient charge-to-spin conversion in CrN system.

We study the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction, i.e., the spin-spin interaction mediated by the second-order expansion in the Kondo coupling, in various Kondo lattice systems. We argue that the weak Kondo coupling expansion contains certain physics that is lost in the usual static approximation to the spin susceptibility. Most notably, while the former is sensitive to time-reversal symmetry breaking, the latter is blind to it. Using exact diagonalization on small systems, we show that this enables inducing spin chirality by an external magnetic field. We argue that within the second-order expansion in the Kondo coupling this effect stems from the odd-in-frequency part of the RKKY interaction, which is lost in the zero frequency approximation. To study larger systems, we use a large-N approximation to capture the effect of the dynamic RKKY interaction on U(1) spin liquids. On a honeycomb Kondo lattice with Haldane fluxes for electrons, we show that a nontrivial topology is induced on the spinons resulting in chiral edge states. Our results suggest that dynamic RKKY in combination with an external magnetic field or in proximity to topological electronic materials, can be used as a replacement for a tunable Dzyaloshinskii-Moriya interaction even in centrosymmetric materials.

We present a general framework to implement massive Nambu-Goldstone quasiparticles in driven many-body systems. The underlying mechanism leverages an explicit Lie group structure imprinted into an effective Hamiltonian that governs the dynamics of slow degrees of freedom; the resulting emergent continuous symmetry is weakly explicitly broken, giving rise to a massive Nambu-Goldstone mode, with a spectral mass gap scaling linearly with the drive period. We discuss explicit and experimentally implementable realizations, such as Heisenberg-like spin models that support gapped spin-wave excitations. We provide a protocol to certify the existence of the massive Nambu-Goldstone mode from the dynamics of specific observables, and analyze the dispersion spectrum and their lifetime in the presence of weak explicit symmetry breaking.

Two-dimensional materials have been recognized as highly promising in next-generation optoelectronic devices and thermal management applications. In this study, we explore two distinct structural phases, $2H$ and $1T$, to elucidate the impact of structural modifications on the electro-optical and thermal transport properties of ${\mathrm{ZrSi}}_2{\mathrm{N}}_4$ monolayer. Our results reveal remarkable differences in the electronic band structure and density of states between the trigonal prismatic ($2H$-phase) and octahedral ($1T$-phase) coordination of Zr atoms. The band gap decreases from 2.736 eV ($2H$ phase) to 2.233 eV ($1T$ phase), accompanied by momentum shift in the valence band maximum at high-symmetry points in the Brillouin zone. Also, the effective masses of electrons and holes are substantially lowered in specific directions for the $1T$ phase indicating improved carrier mobility. Besides, Young's modulus increases while the dielectric constant decreases due to octahedral coordination of Zr atoms in the $1T$ phase. Moreover, the optical absorption spectra are significantly tuned due to distinct charge localization in the respective structural phases. Intriguingly, a notable enhancement in lattice thermal conductivity is observed for the $1T$ phase at room temperature owing to increased phonon lifetimes (reduced anharmonic phonon-phonon scattering rates), increased bonding strength, and phonon group velocities. These results provide comprehensive insights into the phase-dependent electro-optical properties, highlighting their potential in optoelectronic devices. On top of that, the exceptional thermal conductivities and their tunable nature across the two polymorphic forms of ${\mathrm{ZrSi}}_2{\mathrm{N}}_4$ unlock exciting opportunities for designing advanced two-dimensional materials, offering ground-breaking potential in thermal management and heat dissipation technologies.

The complex phase diagram of germanium allows for exotic crystalline phases recoverable from high pressure. Among these, the tetragonal st12 phase is unusual as it shares characteristics with amorphous Ge resulting in desirable band-gap characteristics. Here, we leverage a high neutron flux and large volume pressure capabilities to characterize st12-Ge and its dynamics upon conversion to diamond-cubic Ge with inelastic neutron scattering. We exploit the characteristics of time-of-flight neutron scattering for time-resolved investigations. This analysis may suggest the existence of a transient disordered state upon annealing befitting the known structural relationship between st12-Ge and amorphous Ge, a relationship that can open the potential for band-gap tuning.

The complex surface impedance is a well-established tool to study the super- and normal-fluid responses of superconductors. Fundamental properties of the superconductor, such as the pairing mechanism, Fermi surface, and topological properties, also influence the surface impedance. We explore the microwave surface impedance of spin-triplet ${\mathrm{UTe}}_2$ single crystals as a function of temperature using resonant cavity perturbation measurements employing a multimodal analysis to gain insight into these properties. We determine a composite surface impedance of the crystal for each mode using resonance data combined with the independently measured normal state dc resistivity tensor. The normal state surface impedance reveals the weighting of current flow directions in the crystal of each resonant mode. For ${\mathrm{UTe}}_2$, we find an isotropic $\mathrm{\Delta }\lambda \left(T\right)\sim T^{\alpha }$ power-law temperature dependence for the magnetic penetration depth for $T\le T_c/3$ with $\alpha <2$, which is inconsistent with a single pair of point nodes on the Fermi surface under weak scattering. We also find a similar power-law temperature dependence for the low-temperature surface resistance $R_s\left(T\right)\sim T^{{\alpha }_R}$ with ${\alpha }_R<2$. We observe a strong anisotropy of the residual microwave loss across these modes, with some modes showing loss below the universal line-nodal value, to those showing substantially more. We compare to predictions for topological Weyl superconductivity in the context of the observed isotropic power laws and anisotropy of the residual loss.

Native point defects are fundamental building blocks of defect engineering in thermoelectric materials. However, it remains unclear which changes induced by point defects reduce lattice thermal conductivity ${\kappa }_{\text{l}}$ at the atomic level. This study develops a neural-network potential (NNP) trained on density functional theory data for lead telluride (PbTe) and applies it to equilibrium and perturbed molecular dynamics (PMD) simulations. Isolated Pb and Te vacancies, antisites, interstitials and Schottky pairs are examined using sufficiently large supercells. The NNP is shown to reproduce harmonic and anharmonic vibrational properties and to accurately predict potential energy and atomic forces at finite temperatures. NNP-based PMD simulations reveal that local thermal transport near defects varies significantly depending on the defect type, exhibiting the lowest ${\kappa }_{\text{l}}$ for interstitial Pb. Atom-resolved ${\kappa }_{\text{l}}$ of point defects and their neighboring atoms correlate with the integrated absolute difference in vibrational density of states between those atoms and bulk atoms. This trend appears even within the harmonic approximation, which neglects anharmonic contributions. This suggests that the difference between the harmonic potential energies of pristine and defect-containing PbTe plays a central role in reducing ${\kappa }_{\text{l}}$, by modifying the force field around point defects through the second-order force constant. In contrast, atomic displacements around point defects show a weak correlation with atom-resolved ${\kappa }_{\text{l}}$ and thus may not be a suitable metric for predicting ${\kappa }_{\text{l}}$ of defect-containing PbTe, although relevant quantities are assumed to affect ${\kappa }_{\text{l}}$ in conventional analytical models. The present NNP enables us to analyze physical quantities accessible via molecular simulations with high accuracy and to understand the underlying mechanisms of thermal transport reduction by point defects, without relying on analytical models.