The isothermal evolution of a type-II mesoscopic superconducting cylinder under a magnetic field expansion is analyzed through the standard time-dependent Ginzburg-Landau theory. We calculate the isothermal variation of the entropy, $\mathrm{\Delta }S(T,H)$, by means of Maxwell's relation to show that it reaches a maximum at a temperature $T$ near and below the critical temperature $T_c\left(H\right)$. We show how vortex configurations affect this process, which is the building block of the magnetocaloric effect. The conclusion is that in all situations heat is always absorbed from the environment, qualifying the mesoscopic superconductor as a magnetic refrigerator.

We report a new method for studying magnetism at the atomic level with site selectivity. It is based on the combination of the site-selective diffraction-based x-ray standing wave (XSW) technique and x-ray magnetic circular dichroism (XMCD), which provides the magnetic sensitivity. The use of the standing wave resulting from an interference between the incoming and the Bragg reflected electromagnetic waves ensures that the phase information is not lost and thus brings information about the magnetism at a given site directly. In the paper, we provide the theoretical foundations of such a method based on the dynamical theory of x-ray diffraction and time-dependent perturbation theory. By means of computer simulations, the principle of the method is thus presented in a rather accessible way. Finally, we demonstrate the results of a proof-of-principle experiment on single-crystalline yttrium-iron-garnet (YIG, ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$). We show data exhibiting a clear variation in the XMCD signal caused by the standing wave. A comparison with theoretical functions illustrates that the established theory reliably describes the phenomena involved and allows to extract useful information about the magnetic moments in YIG.

The phenomenon of Anderson localization in various disordered media has sustained significant interest over many decades. Specifically, the Anderson localization of phonons has been viewed as a potential mechanism for creating fascinating thermal transport properties in materials. However, despite extensive work, the influence of the vector nature of phonons on the Anderson localization transition has not been well explored. To achieve such an understanding, we extend a recently developed phonon dynamical cluster approximation (DCA) and its typical medium variant (TMDCA) to investigate spectra and localization of multibranch phonons in the presence of pure mass disorder. We validate the new formalism against several limiting cases and exact diagonalization results. A comparison of results for the single-branch versus multibranch case shows that the vector nature of the phonons does not significantly affect the Anderson transition of phonons. The developed multibranch TMDCA formalism can be employed for studying phonon localization in real materials.

We investigate quantum work statistics within the standard two-point measurement scheme in continuously monitored quantum systems, including the effects of generalized unitary evolution, possibly controlled by quantum circuit models, and multiple generalized measurements as well as postselection of no-click trajectories. We derive an explicit expression for the work generating function that naturally incorporates non-Hermitian dynamics arising from quantum jump processes and reveals deviations from the standard Jarzynski equality due to measurement-induced asymmetries. We illustrate our theoretical framework by analyzing a one-dimensional transverse-field Ising model under local spin monitoring. In this model, increased measurement strength projects the system onto the no-click state, leading to a suppression of energy fluctuations and measurement-induced energy saturation, reminiscent of the quantum Zeno effect. Moreover, we find signatures of the measurement-induced transition observed in the no-click limit in the moments of the work distribution.

Topological lasing is typically enabled by two key mechanisms: effective time-reversal symmetry breaking, which generates the nontrivial topology, and gain-induced non-Hermiticity supplied by the pump. Here we introduce a class of chain-driven lattices where nontrivial Chern numbers emerge directly from the modulation of gain. In this respect, we realize topological lasing-capable models where the pump drives both the lasing action and the topological character of the system. By tuning the modulation period, we identify three distinct regimes: a pseudo-Hermitian regime, a $\mathcal{PT}$-broken phase, and ultimately a domain of topological edge state lasing. Remarkably, the periodic switching of gain can yield topological lasing dynamics on an otherwise trivial static lattice, even under saturable nonlinear conditions, promoting the topologically protected amplification of light. Our system allows for continuous external control between chiral and antichiral edge configurations, enabling codirectional edge transport and protected bulk channels in both broken and unbroken regimes.

Austenitic steel is an attractive construction material for high-temperature applications, with service lifetimes being inversely proportional to metal vacancy diffusion rates. Despite the ubiquity of austenitic steel, there remains significant disagreement in how to calculate Fe vacancy formation and vacancy migration energies due to ambiguity in how to model the Fe paramagnetic (PM) ordering. Specifically, density functional theory (DFT) can efficiently adopt either nonmagnetic (NM) and spin-polarized (SP) approaches, but not directly access the disordered state of PM ordering. This study uses a combination of DFT, Ising models, and kinetic Monte Carlo (KMC) simulations to elucidate the proper magnetic structure that should be used in simulating austenitic Fe and the resulting diffusion rates. Ising models based on DFT spin-flip energetics show Fe vacancies stabilize local ferromagnetic (FM) domains, and that these domains exist up to the melting temperature even without the presence of a vacancy. Thus, SP calculations which collapse into FM ordering should be used in DFT calculations. DFT calculations demonstrate that FM lowers the vacancy hopping barrier $E_v^m$ compared to NM calculations. Further, KMC results demonstrate that >99.9% of vacancy hops occur in local FM domains. Overall, this work demonstrates that vacancy formation and hopping are best modeled by FM-initialized SP calculations in fcc Fe, and by extension in austenitic stainless steel. It also lays the foundation for appropriate vacancy migration modeling in other materials operated within their PM temperature ranges.

The spin-splitting symmetries of altermagnets, such as $d, g$, and $i$ wave, are strictly constrained by the spin point group symmetries of their underlying Euclidean crystal lattices. This raises a fundamental question: Can we transcend this crystallographic constraint to create entirely new magnetic symmetries by manipulating the intrinsic geometry of space? Here, we develop a general theoretical framework for introducing altermagnetic order on hyperbolic Bravais lattices, which are characterized by negative curvature. We discover spin-splitting patterns with exceptionally high-fold symmetries, such as fourfold $g$ wave, 10-fold $m$ wave, and even higher orders. The symmetries of these patterns are directly dictated by the non-Abelian Fuchsian groups describing hyperbolic translations and are unattainable in Euclidean space. Furthermore, we uncover an unexpected spin degeneracy in hyperbolic altermagnets. This degeneracy is not protected by symmetry but originates from flat bands induced by the unique connectivity of the hyperbolic lattice, which arise from the local destructive interference of wave functions. This work not only extends the concept of altermagnetism from flat to curved space but also opens an avenue for designing spin phases through geometry engineering, providing a theoretical platform to explore the profound connections among geometry, magnetism, and electronic properties.

A large variety of materials can be approximately described by means of spin-1/2 Heisenberg ladders. Here, the Density Matrix Renormalization Group algorithm together with a previously established numerical self-consistent mean-field approximation is used to investigate the magnetic properties of spin ladders coupled in a second dimension. The full ground-state phase diagram including spin-gapped, antiferromagnetic, ferrimagnetic, and fully polarized phases is presented as a function of interladder and intraladder coupling and magnetic field. Measurement of the dependence of magnetization on applied magnetic field is shown to enable location of a material on the phase diagram and determination of the Hamiltonian parameters. These results provide a practical route toward identifying and characterizing magnetic materials composed of coupled spin ladders.

Neodymium (Nd) magnets (${\mathrm{Nd}}_2{\mathrm{Fe}}_{14}\mathrm{B}$) are important permanent magnets due to their strong coercive force, which contributes to high-efficiency energy conversion technologies. This coercivity is often enhanced by substituting dysprosium (Dy). Therefore, understanding the magnetic properties of Dy-substituted systems, ${\left({\mathrm{Nd}}_{1-x}{\mathrm{Dy}}_x\right)}_2{\mathrm{Fe}}_{14}\mathrm{B}$, is essential. We investigate the spin reorientation transition in ${\left({\mathrm{Nd}}_{1-x}{\mathrm{Dy}}_x\right)}_2{\mathrm{Fe}}_{14}\mathrm{B}$ using a recently developed atomistic modeling approach. This modeling method captures the microscopic mechanisms of magnetic interactions and temperature effects, including thermal fluctuations. We study the $x$ dependence of the spin reorientation transition temperature ($T_{\mathrm{SR}}$) and the canting angle ($\theta$) of the total magnetization using an importance-sampling Monte Carlo method, based on a model with microscopic parameters derived primarily from first-principles calculations. Our estimates of $T_{\mathrm{SR}}$ and $\theta$ are consistent with experimental results. We also compare our results with those obtained from a previous mean-field-like study and show significant differences, particularly at higher Dy concentrations. Our model more accurately captures experimental trends in this regime. We attribute this improvement to more accurate representations of canting angles and anisotropy energies of the constituent atoms. Additionally, we investigate an anomalous behavior in the total magnetization of ${\left({\mathrm{Nd}}_{1-x}{\mathrm{Dy}}_x\right)}_2{\mathrm{Fe}}_{14}\mathrm{B}$. We find a nondifferentiable point in the magnetization at $T_{\mathrm{SR}}$, which becomes more pronounced with increasing $x$, peaking at $x=0.5$. We discuss the origin of this anomaly in detail through an analysis of the magnetic properties of the constituent atoms.

First-principles computational methods can predict the superconducting critical temperature $T_c$ of conventional superconductors through the electron-phonon spectral function. Full convergence of this quantity requires Brillouin-zone integration on very dense grids, presenting a bottleneck to high-throughput screening for high-$T_{\mathrm{c}}$ systems. In this work, we show that an electron-phonon spectral function calculated at low cost on a coarse grid yields accurate $T_c$ predictions, provided the function is rescaled to correct for the inaccurate value of the density of states at the Fermi energy on coarser grids. Compared to standard approaches, the method converges rapidly and improves the accuracy of predictions for systems with sharp features in the density of states. This approach can be directly integrated into existing materials screening workflows, enabling the rapid identification of promising candidates that might otherwise be overlooked.

In contrast to the usual bulk-boundary correspondence, topological states localized within the bulk of the system have been numerically identified in quasicrystalline structures, termed bulk localized transport (BLT) states. These states exhibit properties that are different from edge states, with one example being that the number of BLT states scales with the system size, while the number of edge states scales with the system perimeter. Here, we define a procedure to identify BLT states, which is based on the physically motivated crosshair marker and robustness analyses. Applying the procedure to the Hofstadter model on the Ammann-Beenker tiling, we find that the BLT states appear mainly for magnetic fluxes within a specific interval. While edge states appear at low densities of states, we find that BLT states can appear at many different densities of states. Many of the BLT states are found to have real-space localization that follows geometric patterns characteristic of the given quasicrystal. Furthermore, BLT states can appear both isolated and in groups within the energy spectrum, which could imply greater robustness for the states within such groups. The spatial localization of the states within a certain group can change, depending on the Fermi energy.

Electronic scattering is a powerful tool to identify underlying changes in electronic behavior and incipient electronic and magnetic orders. The nematic and magnetic phases are strongly intertwined under applied pressure in FeSe, however, the additional isoelectronic substitution of sulfur offers an elegant way to separate them. Here we report the detailed evolution of the electronic and superconducting behavior of ${\mathrm{FeSe}}_{0.96}{\mathrm{S}}_{0.04}$ under applied pressure via longitudinal magnetoresistance studies up to 15 T. At intermediate pressures, inside the nematic phase, the resistivity displays an upturn in zero magnetic field, which is significantly enhanced in the magnetic field, suggesting the stabilization of a spin-density wave phase, which competes with superconductivity. At higher pressures, beyond the nematic phase boundaries, the resistivity no longer displays any clear anomalies in the zero magnetic field, but an external magnetic field induces significant upturns in resistivity reflecting a field-induced order, where superconductivity and magnetic anomalies are enhanced in tandem. This study highlights the essential role of high magnetic fields in stabilizing different electronic phases and revealing a complex interplay between magnetism and superconductivity tuned by applied pressure in ${\mathrm{FeSe}}_{1-x}{\mathrm{S}}_x$.

We present exact analytical solutions for topological edge states, including zero modes and in-gap states, in one-dimensional non-Hermitian quadripartite Su-Schrieffer-Heeger lattices under open boundary conditions. From these solutions, we obtain explicit asymptotic expressions for the edge-state energies and wave functions, and establish rigorous criteria governing their existence and spatial localization. Our results reveal how and under what conditions the non-Hermitian skin effect suppresses or delocalizes edge states through parameter-dependent decay lengths. Furthermore, we introduce for such systems a unified set of topological invariants that not only classify all edge states and restore the bulk-boundary correspondence, but also predict their spatial localization directions. This work thus paves the way for understanding and engineering topological phenomena in a broad class of non-Hermitian multipartite systems, even including those lacking chiral symmetry.

We present a comprehensive experimental study of the neutral donor to donor-bound exciton transition (${\mathrm{D}}^0\to {\mathrm{D}}^0\mathrm{X}$) in isotopically enriched ${}^{28}\mathrm{Si}$, focusing on the group V donors P, As, and Sb under finely tuned uniaxial stress along the [100] and [110] crystal axes and magnetic fields from 3.5 mT to 1.7 T. From these measurements, donor-specific deformation potentials are extracted. The uniaxial electron deformation potential ${\mathrm{\Xi }}_{\mathrm{u}}$ is found to be significantly larger than values reported for other states or transitions in silicon and shows clear dependence on the donor species, indicating an increased sensitivity of the ${\mathrm{D}}^0\mathrm{X}$ state to strain and central-cell effects. We also observe a magnetic field dependence of the hole shear deformation potential $d$, suggesting a more complex strain coupling mechanism than captured by standard theory. Diamagnetic shift parameters determined from Zeeman spectra show good agreement with earlier measurements. Our results provide a refined parameter set critical for the design of silicon quantum devices based on ${\mathrm{D}}^0\mathrm{X}$ transitions.

Bound states in the continuum (BICs) are spatially confined modes that coexist within the continuous spectrum propagating in the medium. The combination with topological physics gives rise to the topological BICs, which inherit the characteristics of traditional BICs and also have the features of topological protection. Here, we report the spin-dependent topological BICs that can support antihelical edge transport modes in a phononic crystal. We employ two decoupled spin subspaces as a bridge to topological BICs, which not only enable the spin-dependent topological BICs but also exhibit novel transport properties, antihelical edge transport. We experimentally realize the spin-dependent topological BICs in a phononic crystal and observe their hallmark, antihelical edge states embedded in the bulk structure with opposite spin. Furthermore, by tuning the interlayer coupling strengths, we experimentally achieve the independent modulation of the two topological BICs with different spins, giving rise to a hybrid system where spin-dependent topological BICs and topological flat bands coexist. Our work deepens the understanding of constructing topological BICs via spin subspaces and opens new avenues for hybrid multimode transport.

We develop a symmetry-based framework to compute band-geometric quantities in multiband systems whose low-energy Hamiltonians realize arbitrary $\text{SU}\left(2\right)$ representations. Exploiting the existence of a quantization axis, we use the Wigner-Eckart theorem to identify the allowed matrix elements and obtain compact analytic expressions for the quantum geometric tensor, the orbital magnetic moment, and the associated orbital transport coefficients. The formalism applies to multifold fermions as well as to gapped $\text{SU}\left(2\right)$ models. Its versatility is illustrated through explicit calculations in representative $\text{SU}\left(3\right)$ and $\text{SU}\left(4\right)$ settings, where orbital Edelstein and orbital Hall responses emerge naturally from the antisymmetric components of the band geometry. These results establish a direct connection between the algebraic structure of the Hamiltonian and intrinsic orbitronic phenomena.

Structured optical fields can be used for the injection and control of charge and spin-valley currents. Here, we present a systematical study of these phenomena for interband absorption of structured light in two-dimensional Dirac materials. We derive general expressions for the current density and the quasiclassical generation rate of photoelectrons in the momentum, coordinate, and spin-valley spaces. We reveal mechanisms of the current formation determined by the local and nonlocal contributions to the optical generation, including the mechanisms related to optical alignment of electron momenta by linearly polarized light, optical orientation by circularly polarized light, and the class of charge and spin-valley photon drags sensitive to the phase and polarization profiles of the optical field. We develop a kinetic theory of electric and spin-valley currents driven by the optical field with spatially inhomogeneous intensity, polarization, and phase and obtain analytical expressions for the current contributions. The theory is applied to analyze the photocurrents emerging in transition-metal dichalcogenide layers and graphene excited by polarization gratings.

The nonlinear Hall effect has attracted considerable attention and undergone extensive investigation in recent years. However, theoretical studies addressing size-dependent effects remain largely unexplored. In this work, we establish a unified semiclassical framework based on the Boltzmann transport equation, incorporating generalized boundary conditions to bridge the ballistic and diffusive transport regimes. Our analysis reveals that the nonlinear Hall effect arises from the combined action of two distinct mechanisms: the Berry curvature dipole (diffusive limit) and the difference between the integrals of the Berry curvature over the two halves of the Fermi surface (ballistic limit). Furthermore, we investigate the Hall effect in the (001) surface states of the topological crystalline insulators SnTe and (Pb,Sn)Se, elucidating that the size dependence originates from the competition between the two transport mechanisms. By connecting the two distinct regimes, our theoretical framework provides a comprehensive understanding of the nonlinear Hall effect in finite-sized systems, offering both fundamental insights and a useful analytical tool for more size-dependent investigations.