We present a comprehensive study of the low-temperature magnetism and field-tuned thermodynamics of the layered Shastry-Sutherland compound ${\mathrm{Eu}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$. ${\mathrm{Eu}}^{2+}$ ions ($4f^7, S=7/2$) form a quasi-two-dimensional orthogonal-dimer network, realizing a large-spin Heisenberg system on a Shastry-Sutherland geometry that is prone to geometric frustration. Magnetic susceptibility and magnetization measurements reveal nearly isotropic ${\mathrm{Eu}}^{2+}$ moments with weak antiferromagnetic interactions. Specific-heat data uncover a primary long-range ordered state at $T_{\mathrm{N}1}=0.8\mathrm{K}$ and a second anomaly near $T_{\mathrm{N}2}=1.0\mathrm{K}$ that is rapidly suppressed by magnetic field, suggesting that it is more field sensitive and may not correspond to an independent thermodynamic phase transition. By separating the magnetic heat capacity, we determine the full magnetic-entropy surface $S_{\mathrm{m}}(T,B)$, which captures the smooth field-driven evolution from the ordered state to a correlated and eventually polarized paramagnetic regime. The resulting isentropic trajectories demonstrate efficient adiabatic demagnetization, allowing cooling from 1.5–3.1 K at 5 T to minimum temperatures of 0.21–0.50 K. Comparison with the benchmark refrigerant ${\mathrm{Gd}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$ shows that ${\mathrm{Eu}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$ exhibits enhanced sub-Kelvin magnetic heat-storage capacity, reflecting its large accessible spin entropy and weak interactions. These results establish ${\mathrm{Eu}}_2{\mathrm{MgSi}}_2{\mathrm{O}}_7$ as a rare example of a Eu-based frustrated magnet that combines weak interactions, a well-resolved low-temperature ordered state, and tunable thermodynamics suitable for sub-Kelvin cryogenic applications.

Chemical substitution offers an effective route to tune magnetic ordering and magnetocaloric performance in rare-earth (RE) oxides for cryogenic refrigeration. Here, we investigate the structural evolution, magnetic properties, and magnetocaloric effect of polycrystalline zircon-type ${\mathrm{Gd}}_{1-x}{\mathrm{Er}}_x{\mathrm{VO}}_4$ $(x=0, 0.1, 0.25, 0.5, \text{and} 0.75)$. Powder x-ray diffraction confirms that all samples crystallize into the tetragonal zircon structure without detectable impurity phases. Substitution of ${\mathrm{Gd}}^{3+}$ by the smaller ${\mathrm{Er}}^{3+}$ ion produces a systematic lattice contraction and modifies the magnetic behavior of the RE sublattice. The magnetic ordering temperature is suppressed from 3.65(2) K in ${\mathrm{GdVO}}_4$ to 2.76(2) K in ${\mathrm{Gd}}_{0.9}{\mathrm{Er}}_{0.1}{\mathrm{VO}}_4$, accompanied by a weakening of the spin-flop-like field-induced anomaly observed in the parent compound. A low Er concentration correspondingly improves the low-temperature magnetocaloric performance, with ${\mathrm{Gd}}_{0.9}{\mathrm{Er}}_{0.1}{\mathrm{VO}}_4$ exhibiting a maximum magnetic entropy change of 45.1 $\mathrm{J}{\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$ for ${\mu }_0\mathrm{\Delta }H=7\mathrm{T}$. These results demonstrate that weak Er substitution effectively tunes the competition among exchange interactions, dipolar coupling, and magnetic anisotropy, optimizing the balance between magnetic ordering and available spin entropy in zircon-type RE vanadates, which is crucial for developing efficient cryogenic refrigeration materials.

We present an in-depth analysis of the orbital magnetism by means of the so-called modern theory based on the Berry phase across distinct classes of materials-$d$ transition-metals, $sp$ metals, and transition metal dichalcogenides—highlighting the importance of the microscopic nature of band structure characteristics on the orbital magnetization. We adopt a gauge-covariant formulation of the modern theory proposed in Lopez et al. [Phys. Rev. B 85, 014435 (2012)], which enables the calculation of orbital magnetism in a controlled manner in any chosen gauge of Wannier functions and gives the total contribution as a gauge-invariant measurable. This captures consistently the contributions due to the anomalous position, velocity, and orbital angular momentum of a Wannier basis, as well as the contributions due to Hamiltonians such that their sum is gauge-invariant. For $d$ transition metals, we find that the atom-centered approximation captures the majority of the total contribution given by modern theory, which we attribute to the localized nature of $d$ electrons. However, $5d$ metals tend to exhibit relatively larger deviation between the two methods than $3d$ metals do, as $5d$ electrons are more delocalized than $3d$ electrons. On the other hand, $sp$ metals exhibit a strong deviation between the two methods, where the large kinetic energy of $sp$ electrons is important. Finally, in $1\mathrm{H}\text{−}{\mathrm{MoS}}_2$, we find that the valley orbital moment at each valley far exceeds the atomic limit orbital moment of $d$ electrons due to coherent hybridization between valence and conduction bands in direct band gaps. Our work elucidates the interplay of the chemical nature of electronic orbitals and the effect of band structures in a consistent manner and highlights the role of the Berry phase in orbital magnetism. The results suggest a promising direction of orbitronics beyond controlling atomic orbitals, in which the orbital magnetism can be greatly enhanced by exploiting the Berry phase.

We examine how an anomalous Josephson current influences odd-frequency superconducting correlations in two Josephson junction geometries. The first consists of two ferromagnetic layers between conventional $s$-wave superconductors, with magnetizations along the $x$ and $y$ axes, forming a bilayer junction. The second contains three ferromagnetic layers between two $s$-wave superconductors, with magnetizations along the $x, y$, and $z$ axes, forming a trilayer junction. Both systems are analyzed in the short- and long-junction limits. In the bilayer case, where no anomalous Josephson current is present, odd-frequency equal-spin triplet correlations develop pronounced peaks at finite magnetizations in the short-junction limit for both tunneling and transparent ferromagnetic interfaces. The odd-frequency mixed-spin triplet correlations also exhibit peaks at finite magnetizations for tunneling ferromagnetic interfaces, whereas for transparent ferromagnetic interfaces they display both peaks and zeros. In the trilayer case, where an anomalous Josephson current exists, similar peaks in both equal- and mixed-spin odd-frequency triplet correlations occur at finite magnetizations for tunneling and transparent ferromagnetic interfaces. The spatial profiles of these correlations remain largely unaffected by the anomalous Josephson current. The Josephson diode efficiency is finite and reaches its maximum at magnetizations corresponding to the peaks of the anomalous Josephson current. Overall, our results show that the anomalous Josephson current has only a marginal influence on odd-frequency spin-triplet pairing. This indicates that the emergence of odd-frequency correlations and the Josephson diode effect are largely independent phenomena, contrary to earlier conjectures. Analysis of the long-junction limit leads to the same qualitative conclusions for both configurations.

Vortex motion plays a central role in determining the resistance of two-dimensional superconductors, both in the context of the Berezinskii-Kosterlitz-Thouless (BKT) transition and in the mixed state of type-II superconductors under magnetic fields. In this study, we introduce an anisotropic pinning potential to investigate vortex-induced resistance across the BKT transition and the upper critical field $H_{c2}$ transition. Our results demonstrate that the anisotropic pinning potential gives rise to distinct critical temperatures and upper critical fields along two orthogonal directions of current transport. These findings provide a general route toward the realization of multiple “critical temperatures” in two-dimensional superconductors.

The application of epitaxial strain to perovskite thin films has emerged as a powerful tool for tuning their properties, with differences observed between (001)- and (111)-oriented films. Although these effects have been extensively studied in ${AB\mathrm{O}}_3$ perovskites, the influence of strain on double perovskites remains comparatively underexplored. We present first-principles calculations that investigate the impact of strain on (001)- and (111)-oriented films of the $B$-site ordered double perovskite ${\mathrm{Pb}}_2{\mathrm{CoTeO}}_6$. For both film orientations, we identify a strain-induced transition in the ground state at a small tensile strain, corresponding to a change between phases with distinct octahedral rotation patterns. By analyzing the evolution of bond angles and bond lengths as a function of strain, we correlate these structural changes with the resulting ground-state transitions. Our results demonstrate that epitaxial strain provides an effective route for controlling the ground-state phase of $B$-site ordered double perovskites.

${\mathrm{Ni}}_2\mathrm{MnGa}$ is regarded as a prototypical shape memory Heusler alloy (SMHA) due to its large magnetic field-induced strain ($\sim 10\%$) and multifunctional properties. The ${\mathrm{Ni}}_2\mathrm{MnGa}$ undergoes a transition from a high-temperature austenite phase to a low-temperature martensitic (MT) phase via a precursor or premartensite (PM) phase transition. The PM phase plays an important role in understanding the origin of the structural phase transition in ${\mathrm{Ni}}_2\mathrm{MnGa}$. However, the lack of a PM phase in the epitaxial thin films of ${\mathrm{Ni}}_2\mathrm{MnGa}$ left an issue of the origin of modulation unresolved. Here, we investigated the temperature-dependent anomalous Nernst effect (ANE) in an epitaxial thin film of ${\mathrm{Ni}}_2\mathrm{MnGa}$ where a clear PM phase transition was observed together with the martensite phase transition. A systematic analysis of the anomalous Nernst thermopower ($S_{\text{ANE}}$) and anomalous Nernst conductivity (${\alpha }_{xy}^{\text{ANE}}$) was performed across all the phases (austenite, PM and martensite). A sharp change in $S_{\text{ANE}}$ and ${\alpha }_{xy}^{\text{ANE}}$ at the PM phase is observed. With ${\alpha }_{xy}^{\text{ANE}}$ being sensitive to the changes at the Fermi surface, this establishes the link of soft phonon mode and structural modulation in ${\mathrm{Ni}}_2\mathrm{MnGa}$.

The global optimization of atomic clusters represents a fundamental challenge in computational chemistry and materials science due to the exponential growth of local minima with system size (i.e., the curse of dimensionality). We introduce a framework that overcomes this limitation by exploiting the low-rank structure of potential energy surfaces through tensor train (TT) decomposition. Our approach combines two complementary TT-based strategies: the algebraic TTOpt method, which utilizes maximum volume sampling, and the probabilistic PROTES method, which employs generative sampling. A key innovation is the development of physically constrained encoding schemes that incorporate molecular constraints directly into the discretization process. We demonstrate the efficacy of our method by identifying global minima of Lennard-Jones clusters containing up to 45 atoms. Furthermore, we establish its practical applicability to real-world systems by optimizing 20-atom carbon clusters using a machine-learned moment tensor potential, achieving geometries consistent with quantum-accurate simulations. This work establishes TT decomposition as a powerful tool for molecular structure prediction and provides a general framework adaptable to a wide range of high-dimensional optimization problems in computational material science.

The electric field rising time $t_r$ is frequently overlooked in ultrafast ferroelectric switching studies, despite its critical role in switching dynamics and mechanism discrimination. Using stochastic phase-field simulations of ${\text{BaTiO}}_3$, we systematically investigate $t_r$ effects on four switching mechanisms identified in our prior work [Wen et al., Phys. Rev. B 108, 134114 (2023)]. Our results reveal distinct mechanism-dependent behaviors: $t_r$ acts as a temporal offset in the Smoluchowski-diffusion mechanism, suppresses inertial switching in the relaxation-control mechanism, and drives a transition from field-driven to thermally assisted in the ultrafast-switching mechanism. By decoupling rising-time-induced relaxation, we extract the intrinsic switching time and show that $t_r$ can significantly alter extracted Merz's law parameters ($t_0, E_a$). This work establishes $t_r$ as a pivotal control parameter and underscores its essential incorporation into both experimental characterization and theoretical modeling of ultrafast ferroelectric switching.

Complementary media predicted by transformation acoustics provide a powerful route to acoustic wave manipulation through deterministic spatial cancellation. However, their experimental realization in airborne acoustics has remained elusive due to the stringent requirement of simultaneously engineering spatially varying negative effective mass density and bulk modulus. In this paper, we implement a step-layered double-negative metamaterial (SLDNM) to construct a complementary-media-based acoustic superscatterer. The required extreme effective parameters are successfully realized via the overlapping excitation of monopolar and dipolar resonances within each layer of the SLDNM. We tailored the scattering boundary of the complementary-media-based acoustic superscatterer deterministically in experiments, creating a virtual boundary three times larger than its physical size at 800 Hz in a two-dimensional airborne sound waveguide. Upon integration with the complementary-media-based acoustic superscatterer, we further experimentally demonstrated omnidirectional radiation suppression of a dipolarlike source placed at the virtual boundary. This work fills a longstanding gap between theoretical proposals and experimental realizations of complementary media in acoustics.

Chalcohalides compounds represent a promising class of optoelectronic materials. Among them, $Q\mathrm{SeI}$ $(Q=\mathrm{In}, \mathrm{Ga}, \mathrm{Al})$ stands out due to its one-dimensional van der Waals structure and helical chain configuration. In this study, we investigate the pressure-tunable optical and electronic properties of InSeI. Optical absorption measurements reveal a rapid narrowing of the band gap at a rate of −0.1 eV/GPa, followed by a sharp collapse of 0.4 eV above 4.1 GPa. Meanwhile, the sample exhibits a striking color change from yellow to black, indicative of pronounced piezochromic behavior. Electrical transport measurements uncover an insulator-to-metal transition at 37.8 GPa, followed by the emergence of superconductivity with a critical temperature $\left(T_{\mathrm{c}}\right)$ of $\sim 5.8\mathrm{K}$. Synchrotron x-ray diffraction and Raman spectroscopy reveal that pressure-induced amorphization occurs at relatively low pressures, involving primarily intrachain disorder, which accounts for the abrupt band-gap reduction and coloration change. Upon further compression, the tubular framework collapses, and long-range disorder gives rise to a possible polyamorphic transformation, leading to metallization and superconductivity. The tunable tubular-chain structure and associated polyamorphism make InSeI a promising platform for optoelectronic application, such as optical switches, broadband absorbers, and pressure-sensitive photonic devices, and provide a fertile ground for exploring polyamorphic superconductivity in low-dimensional chalcohalide systems.

We analyze mechanisms for universal out-of-equilibrium dynamics near criticality by exploring the effect of randomized quantum resetting (QR) under a linear finite-time drive across, or very close to, an equilibrium quantum critical point. Using the transverse-field Ising chain as a minimal model and exploiting its exact solution, QR is found to cause a crossover of the scaling of the defect density with the time scale $\tau$ of the drive, from Kibble-Zurek to anti-Kibble-Zurek scaling as $\tau$ increases. Depending on whether the ramp ends in a symmetry-broken phase or not, the resulting defects are topological or nontopological. The competition between QR and the Kibble-Zurek mechanism gives rise to local minima of the defect densities at optimal annealing times. These times and the corresponding local minima are shown to scale as universal power laws with the rate of QR. Additional results for the scaling of the mean excess energy suggest that a system driven across, or very close to, a quantum critical point exhibits the same scaling behavior under a linear finite-time drive with QR as with uncorrelated noise. We suggest that these results may serve as benchmarks for validating quantum annealing devices.

A coupled simulation scheme combining Maxwell equations with semiclassical electronic and molecular dynamics based on the electron force field model has been developed to enable the description of interaction dynamics among electrons, ions in a condensed matter, and electromagnetic waves at a practical computational cost. This method is applied to investigate laser ablation of a silicon thin film induced by intense 100-fs pulsed laser irradiation. The simulation with normal incidence shows that a highly elevated electron temperature caused by light absorption leads to the initial ejection of electrons from a surface after the pulse has passed, facilitated by enhanced thermal fluctuations and a destabilized structure at the surface induced by energy relaxation. Subsequently, the positive net charges at the disordered surfaces, resulting from missing electrons, cause a Coulomb explosion of the surface ions accompanied by electrons. The explosive expansion of the vapor leads to the formation of small cavities and further inhomogeneous vapor-vacuum separation during the phase explosion process. Thus, the presented simulation provides a comprehensive microscopic understanding based on interaction dynamics among electrons, ions, and light within the semiclassical framework.

We investigate the physical consequences of having a spectrum that satisfies random matrix theory (RMT) for generic Lindbladians, and compare its implications for spatially local and completely random Lindblad dynamics in one spatial dimension. We find that Lindbladians whose spectrum is described by RMT exhibit quasiuniversal early-time dynamics for quantities nonlinear in the density matrix, in the sense that for generic, highly entangled initial states, the early time evolution is independent of the choice of initial state. We numerically investigate how locality generically imposes constraints on the size-dependence of Lindblad eigenoperators. This size dependence implies that linear observables, such as expectation values of local operators, are highly sensitive to eigenmodes outside the bulk of the spectrum in the thermodynamic limit, and plays a central role in limiting operator growth in the presence of dissipation. We find that when single-site dissipation dominates, an operator's decoherence scales approximately linearly with its Pauli weight, even in the presence of two-site jump operators. When two-site only dissipation dominates, however, this generic trend in operator size can be violated for numerically accessible system sizes, leading to long-lived high Pauli-weight operators.

Nonlinear phononics provides a route to control crystal structures through light-induced phonon excitation. In this study, we apply nonlinear phononics to an iron-based superconductor, LaFeAsO, with the aim of tuning its crystal structure toward the ideal one to enhance superconductivity. We simulate light-induced phonon dynamics on the anharmonic lattice potential determined by first-principles calculations. We find that the anion height $h$, a key structural parameter in iron-based superconductors, approaches its ideal value when an appropriate infrared-active phonon mode is selectively excited. This result suggests the possibility of controlling crystal structures and enhancing superconductivity in iron-based superconductors based on the concept of nonlinear phononics.

We study a so-called semiergodic brickwork dual-unitary circuit where, in the infinite volume limit, the two-point correlation functions of single-site operators exhibit ergodic behavior along one light ray and nonergodic behavior along the other light ray. Here, however, we study intermediate and long-time dynamics of a system in a finite, large volume. Under such dynamics, the Heisenberg evolution of a single traceless single-site operator lies within a restricted subspace, and this time evolution can be mapped to a simpler problem of a single qutrit scattering with a bunch of qubits sequentially. Despite the model being nonintegrable and free from any quenched disorder, the operator entanglement grows at most logarithmic in time, contrary to prior expectations. The autocorrelation function can be written in terms of a sum of products of $SO\left(3\right)$ matrices, allowing for a random matrix prediction for the autocorrelation function at late times. The operator size distribution also becomes bimodal at certain times, displaying intermediate behavior between chaotic and free systems.

We investigated the magnetic ordering, crystal lattice distortion, and spin dynamics in the magnetocaloric material $\mathrm{Ho}{\mathrm{B}}_2$ using neutron and x-ray diffraction (XRD), along with AC susceptibility measurements. Although $\mathrm{Ho}{\mathrm{B}}_2$ exhibits a ferromagnetic phase transition at $T_1=15\mathrm{K}$, the phase transition at $T_2=11\mathrm{K}$ has not yet been elucidated. In high-resolution powder neutron diffraction and single-crystal XRD experiments, we observed a structural phase transition from hexagonal ($P6$/mmm) to monoclinic ($C2/m$) at $T_2$. The structural change occurred concomitantly with a change in the moment size and the fixing of the spin orientation angle of the $\mathrm{H}{\mathrm{o}}^{3+}$ moments below $T_2$. Analyzing the structural distortion mode coupled to the spin direction, we found that the ferromagnetically ordered moments lie in the hexagonal ($x$, −$x, z$) plane. In the AC susceptibility measurements, we observed a large enhancement in susceptibility along the $ab$ plane for $T_2<T<T_1$, indicating that the ferromagnetic state in the intermediate-temperature region is characterized by large spin fluctuations. Considering the observed symmetry lowering in the crystal structure combined with the previously reported crystal electric field levels for the $4f$ orbitals of $\mathrm{H}{\mathrm{o}}^{3+}$, we propose that the lower-temperature phase transition can be understood by the rearrangement of the $4f$ orbital state with monoclinic symmetry.

We present a first-principles investigation of the electronic structure, lattice dynamics, electron-phonon coupling, and superconducting properties of the hexagonal kagome-lattice compound ${\mathrm{Re}}_2\mathrm{Zr}$, in which time-reversal symmetry breaking and unconventional pairing were recently proposed. We examine whether superconductivity in ${\mathrm{Re}}_2\mathrm{Zr}$ can be explained within a conventional phonon-mediated framework by performing fully ab initio calculations within the density functional theory for superconductors. The electronic structure is characterized by a mixture of seven two- and three-dimensional Fermi surface sheets, giving rise to multiband superconductivity with many overlapping superconducting gaps. A spin-orbit-induced Van Hove singularity is identified in the density of states near $E_F$. The electron-phonon interaction is moderately strong, with a coupling constant $\lambda \simeq 0.88$. Superconducting gap calculations reveal significant anisotropy and a broad distribution of gap values across different Fermi surface sheets. Spin fluctuations introduce additional depairing effects and reduce the critical temperature from 7.7 to 6.4 K, in excellent agreement with the experimental value of 6.65 K. Taken together, our results show that the superconducting energy scale in ${\mathrm{Re}}_2\mathrm{Zr}$ can be quantitatively reproduced within a conventional phonon-mediated framework, while the resulting state exhibits pronounced multiband and anisotropic gap structure. The origin of the experimentally suggested time-reversal symmetry breaking, however, remains an open question.

We study quantum magnetometry based on phase-estimation algorithms in a sensor formed by a superconducting qubit coupled to a two-level system (TLS). Using Ramsey interferometry with single-shot binary readout, we construct a precomputed calibration pattern $P_0(f_q,\tau ,{\varphi }_m)$ and implement Bayesian learning. The qubit-TLS exchange reshapes the Ramsey response into a time-dependent structured response with revivals, producing pronounced minima and maxima in the Fisher information. The standard Kitaev algorithm probe weakens information at antirevival times, thereby reducing the net information gain and degrading sensitivity. We further introduce a frequency shift corrected algorithm that improves flux and field sensitivities, expands the dynamical range, and lowers the estimation error rate. Our results show that TLS coupling induces a time-selective metrological response not captured by the effective dephasing time, and that calibration-aware interrogation strategies can mitigate or exploit this structure.

The Berry curvature (BC)—a quantity encoding the geometry of electronic wavefunctions—governs various electronic transport effects in quantum materials. In magnetic systems, the BC is reponsible for the intrinsic part of the anomalous Hall conductivity. Local concentrations of BC in noncentrosymmetric materials can lead instead to the quantum nonlinear Hall effect. Here, we argue that the bulk of nonmagnetic metals with inversion symmetry—systems where the BC is forced to vanish at any momentum—can be endowed with substantial concentrations of BC even with an infinitesimally small Zeeman coupling. This Zeeman-activated BC, independent of the magnetic field strength and instead related to the degree of nonparabolicity of the electronic bands, couples to the electronic orbital motion to generate a negative longitudinal magnetoresistance that scales with the relaxation time as the Drude resistivity. We show that the Zeeman-actived BC and the related intrinsic negative magnetoresistivity are generic: they appear in all centrosymmetric point groups and can occur both in topological and conventional conductors.