Nonreciprocal dissipationless transport has long been sought for applications in superconducting technologies. Recently, it has been implemented by the so-called superconducting diode effect. Such an effect arises from an imbalance in critical supercurrents flowing in opposite directions. In this work, we theoretically demonstrate how the superconducting diode effect emerges in the quantum spin Hall phase when brought into full proximity with a superconductor. We explore two regimes: large and narrow quantum wells. In the former geometry, we show that the superconducting diode effect can be externally controlled using both magnetic and electric fields, achieving unit efficiency. In the latter regime, where tunneling between opposite edges may occur, we propose a mechanism for an intrinsic superconducting diode effect driven by edge reconstruction, which does not require external magnetic fields. This phenomenon, which is related to the topological nature of the underlying system, represents one of the few examples of a superconducting diode effect in low dimensions enabled by spontaneous time-reversal symmetry breaking.

Ruddlesden–Popper nickelates exhibit high-temperature superconductivity closely intertwined with charge and spin density waves. However, fundamental questions persist regarding the interplay between the associated density wave (DW) fluctuations and superconductivity, as well as the orbital character and symmetry underlying the DW instabilities. Here, we utilize polarized Raman scattering to investigate the phononic and electronic Raman responses of the trilayer nickelate ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ across its concomitant charge and spin density wave transitions. In addition to distinct phonon anomalies occurring below the transition temperature, we observe a depletion of continuum spectral weight up to 114 meV and a pronounced peak centered at this energy. By combining momentum-selective information from polarized electronic Raman scattering with Raman-response model calculations based on a multiorbital Raman vertex in a reconstructed two-orbital DW state involving both $\mathrm{Ni}\text{−}3d_{x^2-y^2}$ and $\mathrm{Ni}\text{−}3d_{z^2}$ orbitals, we identify 114 meV as the energy scale $2{\mathrm{\Delta }}_{\mathrm{DW}}$ of the DW gap, characterized by incoherent opening and non-mean-field behavior. Furthermore, the model calculations reveal that the corresponding $2{\mathrm{\Delta }}_{\mathrm{DW}}$ peak has a multiorbital origin, requiring both orbital contributions and their mixing beyond single-orbital projections, thus shedding light on the nature of the DW instabilities in ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$.

X-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) are powerful probes of electronic structure owing to their chemical and orbital selectivity. For powder samples, however, interpreting RIXS spectral intensities remains challenging as the measured signal is an average over all orientations. Existing theoretical treatments rely largely on spherical-tensor formalisms, which often involve complex derivations and case-specific analyses. Meanwhile, recent advances in quantum-chemistry methods have made the evaluation of transition tensors in Cartesian coordinates both accurate and straightforward. Here, we present a general theoretical framework that translates Cartesian transition tensors into physically meaningful, orientation-averaged intensities for powder samples. The formalism allows predicting angular and polarization dependences ab initio for both XAS and RIXS and is extendable to other spectroscopies. The resulting predictions show excellent agreement with RIXS experimental data at the Ce ${\mathrm{L}}_3$ edge.

Using time-dependent simulations, we analyze the trajectories of electrons released from a quantum dot in a waveguide made of a spin-orbit-coupled material (InSb). An electron released from the quantum dot, when driven by an electric field follows a trajectory that is deflected by spin-orbit interaction and undergoes spin precession that results in a spin-dependent, snakelike trajectory. The trajectory strongly depends on the initial state of the electron, enabling detection of the electron quantum state in the dot when connected to the T junction. Notably, we show that the snakelike trajectory persists even under a small external magnetic field with low, incomplete initial electron spin polarization. Our findings are supported by semiclassical calculations of the electron trajectory, which show good agreement with full quantum mechanical simulations.

Atomic steps have strong influences on surface two-dimensional superconductors. Josephson vortices formed at the atomic steps under magnetic fields may dominate transport phenomena at low temperatures, but its experimental verification is still lacking. Here, we report the vortex transport properties of the atomic-layer superconductor Si(111)-$(\sqrt{7}\times \sqrt{3})$-In with vicinal surfaces, for which Josephson vortices are directly observed by scanning tunneling microscopy. A sharp drop in resistance with decreasing temperature $T$, detected under out-of-plane magnetic field $B$, reveals a distinctive anisotropy with respect to the atomic step direction. The anisotropy of sheet resistance, proportional to that of vortex mobility, amounts to the order of ${10}^3$ at intermediate magnetic fields. In the high-$T$ and low-$B$ region, Josephson vortices exhibit thermally excited creep motions with anisotropic activation energy $U_{\mathrm{act}}$. A further increase in $B$ suppresses $U_{\mathrm{act}}$ toward zero anisotropically, resulting in one-dimensional pinning-free vortex flow at $0.10\lesssim B\lesssim 0.20\mathrm{T}$. At the lowest temperatures, the vortex motion is governed by quantum tunneling. A $B\text{−}T$ phase diagram constructed based on these measurements reveals multiple regions characterized by directionally dependent vortex-transport mechanisms.

The magnetic Zintl phase ${\mathrm{Eu}}_3{\mathrm{In}}_2{\mathrm{As}}_4$ is theoretically predicted to host an ideal Weyl semimetal state in a ferromagnetic order, which could be induced from its antiferromagnetic ground state by an external magnetic field. Through comprehensive magnetotransport experiments, we investigate its field-induced electronic evolution. While an external magnetic field suppresses the antiferromagnetic order as expected, it drives the system into a forced ferromagnetic state with short-range correlations. This field-induced state exhibits a combination of transport features—a nonsaturating linear magnetoresistance (up to 58.9%), a high carrier mobility ($2.3\times {10}^3\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$), a light cyclotron effective mass ($\sim 0.23m_{\mathrm{e}}$), and a Berry phase close to π. The field-polarized state concurrently shows a profoundly suppressed anomalous Hall effect ($\sim 0.037\times {10}^{-3}\mathrm{m}{\mathrm{\Omega }}^{-1}\mathrm{c}{\mathrm{m}}^{-1}$, which is far less than the theoretical value), which does not support the ideal Weyl semimetal state. Instead, observations point to a field-induced electronic evolution. This comprehensive data set is of interest for understanding field-induced electronic evolution and magnetotransport in Eu-based correlated semimetals.

The quantum well thickness—defined by the number of inorganic layers ($n$)—is a pivotal structural parameter that governs the optoelectronic properties of two-dimensional (2D) perovskites. Despite the established role of quantum well thickness in modulating linear optical responses, the influence on the nonlinear optical conductivity remains largely unexplored. Herein, we report a systematic investigation of terahertz (THz) emission from ${\left(\mathrm{PEA}\right)}_2{\left(\mathrm{MA}\right)}_{n-1}\mathrm{P}{\mathrm{b}}_n{\mathrm{I}}_{3n+1}$ perovskite thin films with controlled quantum well thicknesses ($n=1-4$ and $\infty$) under normal-incidence excitation by a two-color laser field (800 + 400 nm). Our measurements reveal a pronounced inverse correlation between $n$ and THz emission efficiency, directly attributable to enhanced quantum and dielectric confinement at reduced layer numbers. Spectroscopic analysis confirms that the emission arises from a third-order nonlinear optical process, wherein transient photocurrents are generated via quantum interference between single-photon and two-photon absorption pathways. Polarization-resolved THz emission spectroscopy enables quantitative mapping of the nonlinear optical conductivity tensor across the 2D-to-3D structural transition. Notably, by structurally tuning the quantum well thickness $n$ and dynamically controlling the relative polarization angle of the two-color field, we achieve control over the magnitude and direction of the injection photocurrent—and consequently, the polarity of the emitted THz field. This work establishes THz emission spectroscopy as a powerful, contact-free probe of third-order nonlinear conductivity in low-dimensional quantum materials and underscores the promise of 2D perovskites as highly tunable platforms for next-generation THz emitters and nonlinear optoelectronic devices.

Dirac-like cones in photonic crystals typically arise from accidental degeneracies, yet the connection between their emergence and the scattering properties of the constituent particles remains unclear. Here, we establish a Mie scattering—band structure correspondence, demonstrating that such Dirac-like cones are fundamentally related to the Mie scattering properties of an individual particle. Specifically, when the Mie coefficients of an isolated particle satisfy either dipolar duality ($a_1=b_1$) or quadrupolar duality ($a_2=b_2$) at a certain frequency, a photonic crystal composed of such particles with a suitable lattice constant exhibits balanced global electric and magnetic responses. This balance induces the formation of a Dirac-like cone from dipolar or quadrupolar modes at that frequency. This scattering-band correspondence enables a two-step design strategy: first engineering the Mie coefficients of a single particle and then tuning the lattice constant, thereby avoiding computationally costly global optimization. Using this approach, we demonstrate configurable semi-Dirac cones that support unique wave-transport phenomena. Our work directly bridges single-particle scattering behavior and photonic mode degeneracy, providing a powerful route for photonic band engineering.

Ermakov has shown how the solution to the classical harmonic oscillator in one spatial dimension with general time-dependent frequency can be reduced to the time-independent case and an associated nonlinear ordinary differential equation, an analysis that has been applied to the Schrödinger equation as well. We extend this analysis to the Landau problem of a charged particle in a uniform magnetic field in two dimensions, and we construct the generalized Laughlin wave functions for the case when the magnetic field is time-dependent. We also work out the dynamics of density fluctuations [the Girvin-MacDonald-Platzman (GMP) mode] and argue that it is possible to tune the frequency of the magnetic field to obtain a compressible droplet of fermions. We also analyze the dynamics of the edge modes of the droplet for the integer Hall effect.

We present a theoretical study of dipolar-exchange spin waves in antiferromagnetic and altermagnetic thin films using a multilayer model in which both sublattices coexist within the same layer. The calculated dispersion of pure dipolar spin waves agrees well with the established results for uniaxial antiferromagnets. By including exchange fields, we systematically analyze mode evolution, spatial profiles, and precession ellipticity, revealing how the interplay between exchange and dipolar interactions reshapes the spin-wave spectrum, including band crossings and mode hybridizations. Extending the framework to altermagnets with sublattice-dependent anisotropic exchange reveals an angle-dependent mode coupling: A hybridization gap opens for most propagation directions except at a specific angle, where the modes may remain degenerate due to the $d$-wave altermagnetic symmetry. A comparison with a synthetic antiferromagnetic model further highlights the essential role of the model-dependent dipolar field. Our results provide a solid theoretical basis for interpreting and designing spin-wave experiments in antiferromagnetic, altermagnetic, and ferrimagnetic thin films.

We present a theory of the Josephson current in superconductor-normal metal-superconductor (SNS) junctions in the presence of generic spin-dependent fields, such as spin-orbit coupling (SOC), Zeeman fields, and altermagnetism. We consider systems with arbitrary disorder strength, going beyond the usual diffusive and ballistic approximations. Using the linearized quasiclassical Eilenberger equation, we derive a compact expression for the Josephson current, which is then applied to various situations of experimental interest. First, we investigate the evolution of the Josephson critical current in an applied magnetic field in the presence of Rashba and Dresselhaus SOC, and discuss how this dependence can be used to probe SOC in the junction. We then study the anomalous Josephson $\left({\phi }_0\right)$ effect in systems with Rashba SOC and show that it remains robust over a wide range of disorder strength, and can even be enhanced by moderate disorder in sufficiently long junctions. Finally, we investigate the Josephson current in disordered junctions with altermagnets, and show how the $0\text{−}\pi$ transition in such systems is suppressed by disorder. Our results may be useful for describing experimental setups with high-mobility samples, which nevertheless always contain some amount of disorder, and where neither purely ballistic nor diffusive approximations are adequate.

The Peierls instability, the spontaneous dimerization of a one-dimensional metallic chain at half-filling, is a paradigmatic mechanism for charge-density-wave (CDW) formation. Here, we test its robustness under finite doping and interchain hybridization in finite-thickness arrays of identical chains. We find that the stacking geometry plays a decisive role in stabilizing CDW order away from half-filling. Parallel-coupled chains exhibit a bistable regime where the normal and dimerized states coexist as local minima of the total energy, while skew-coupled chains display reentrant CDW order upon doping. Our results demonstrate that even minimal models of coupled atomic chains host rich phase diagrams controlled by doping, lattice rigidity, and interchain coupling geometry.

Singular value decomposition (SVD) provides a convenient way to construct Hermitian-like diagnostics for non-Hermitian many-body systems, but its reliability for locating many-body localization (MBL) transitions remains unclear, particularly in systems preserving time-reversal symmetry (TRS). We benchmark SVD-based diagnostics against exact diagonalization (ED) in TRS-preserving non-Hermitian hard-core-boson chains with nonreciprocal hopping, considering quasiperiodic, random-disorder, and Stark potentials. We compare level statistics, half-chain entanglement entropy, inverse participation ratio, and spectral form factors. For the quasiperiodic and random-disorder models, ED-based entanglement and IPR yield mutually consistent finite-size transition estimates, whereas the corresponding SVD-based estimates are systematically shifted to larger disorder strengths and can lead to different phase assignments. The discrepancy is also reflected in the spectral form factors, where the ED-based dissipative spectral form factor and the SVD-based singular form factor can indicate different spectral regimes at the same parameters. In contrast, for the clean Stark model, ED and SVD give consistent transition estimates. We identify the origin of this model dependence as the fact that SVD probes the auxiliary Hermitian operator ${\widehat{H}}^{†}\widehat{H}$, rather than the intrinsic right-eigenstate structure of $\widehat{H}$; consequently, SVD can be quantitatively reliable only when the corresponding bulk-state structures remain aligned. Our results show that SVD-based diagnostics can capture qualitative RMT-to-Poisson trends, but are not generically reliable quantitative probes of MBL transitions in TRS-preserving non-Hermitian many-body systems.

The recent proposal and observation of spin inertia, and the consequent high-frequency spin nutation mode, have raised key questions for our understanding of magnetization dynamics, especially considering its high relevance for magnetic memories and ultrafast switching. Notwithstanding recent progress, a clear identification of spin inertia's physical origin thereby offering predictive power remains to be accomplished. Here, discussing general principles for identifying this physical origin, we examine unquenched orbital angular momentum (OAM) finding it to be a key candidate, despite its typically small value. Treating OAM and spin within a two-sublattice model, we derive the equivalent single-sublattice framework for magnetization dynamics making appropriate approximations. The latter naturally manifests the spin inertia term and parameter, which are otherwise introduced phenomenologically. The inertia parameter evaluated within our model is found to be in good agreement with its experimentally observed value in cobalt. We further delineate key experimental signatures that could verify or rule out the unquenched OAM as the origin of the observed high-frequency mode, and avoid a spurious optical mode in a two-sublattice ferromagnet from being identified as nutation. Our analysis offers a potential link between the recently emerged fields of orbitronics and spin inertia, thereby motivating investigations at their intersection.

We report a thermally driven structural crossover of vortex matter in a two-dimensional superconducting Penrose quasicrystal. At low temperatures, vortices are pinned by the quasiperiodic lattice, forming an aperiodic pattern. With increasing temperature, vortex-vortex interactions dominate, leading to a conventional triangular Abrikosov lattice. Our findings reveal a tunable interplay between intrinsic pinning and vortex interactions, which leads to intricate vortex structures in superconducting quasicrystals.

Metallic quantum ferromagnets in the absence of quenched disorder are known to generically undergo a first-order quantum phase transition, avoiding the quantum critical point that had originally been expected. This is due to soft modes in the underlying Fermi liquid that lead to long-ranged correlations. These correlations in turn yield a nonanalytic dependence of the free energy on the magnetization even at a mean-field level that results in a fluctuation-induced first-order transition. Kirkpatrick and Belitz [Phys. Rev. Lett. 124, 147201 (2020)] have pointed out that one notable exception are non-centrosymmetric metals with a strong spin-orbit interaction. In such materials the spin-orbit interaction gives the relevant soft modes a mass, which inhibits the mechanism leading to a first-order transition Miserev, Loss, and Klinovaja [Phys. Rev. B 106, 134417 (2022)] have claimed that this conclusion does not hold if electron-electron interactions in the particle-particle channel, or $2k_{\mathrm{F}}$ scattering processes, are considered. They concluded that this interaction channel leads to soft modes that are not rendered massive by the spin-orbit interaction and again lead to a first-order quantum phase transition. In this Comment we show that this conclusion is not correct in three-dimensional magnets if the screening of the interaction is properly taken into account.

We reply to the Comment by D. Belitz and T. R. Kirkpatrick on our article “Instability of the ferromagnetic quantum critical point and symmetry of the ferromagnetic ground state in 2D and 3D electron gases with arbitrary spin-orbit splitting.” They correctly point out that nonanalyticities in the thermodynamic potential $\mathrm{\Omega }$ of 2D and 3D Fermi liquids that originate from the backscattering processes are suppressed by the square of the Cooper logarithm. This suppression is not essential in 2D Fermi liquids where the nonanalyticity is cubic and, therefore, is much more relevant than the quartic Ginzburg-Landau term. However, in 3D Fermi liquids, the Cooper renormalization renders the marginally relevant quartic nonanalyticity marginally irrelevant. We argue that the leading $\mathrm{\Omega }\propto B^{4}ln(E_F/B)$ form of the 3D nonanalyticity in the thermodynamic potential $\mathrm{\Omega }$ as a function of the Zeeman field $B$ survives due to a contribution coming from the arbitrary-angle scattering that is not subject to the Cooper renormalization. In perturbation theory, such a correction first emerges in third order in the interaction, as was identified by Maslov and Chubukov [Phys. Rev. B 79, 075112 (2009)]. However, the sign of this third-order correction is positive, which contradicts the physical argument on the sign of nonanalytic corrections presented by D. Belitz and T. R. Kirkpatrick in their Comment. Maslov and Chubukov argued that the overall sign of the nonanalytic correction is not universal and strongly depends on the angular structure of the Landau scattering amplitude in the regime where the interaction is no longer weak; this is also the regime where the ferromagnetic quantum phase transition is expected. They also showed that the nonanalyticity remains marginally relevant in the vicinity of the 3D ferromagnetic quantum critical point, $\mathrm{\Omega }\propto -B^{4}lnln(E_F/B)$. Though this nonanalyticity can formally destabilize the $T=0$ ferromagnetic quantum critical point, it becomes irrelevant at any experimentally achievable temperature.

The practical application of ${\mathrm{BaCeO}}_3$-based electrolytes is limited by their poor chemical stability in proton-conducting solid oxide fuel cells. Commonly employed $B$-site doping strategies typically improve proton transport with limited improvement in stability. Recent experiments show that $A$-site Ca doping can simultaneously enhance both properties. Here, through first-principles calculations and mechanistic analysis of Ca-doped ${\mathrm{BaCeO}}_3$, we identify the synergistic roles of small-radius, high-electronegativity $A$-site dopants in governing proton transport and chemical stability in perovskite electrolytes. We show that the higher electronegativity of an $A$-site dopant weakens the $A$-O ionic bonding, facilitating oxygen-vacancy formation and enhancing proton uptake by increasing the basicity. This weakened A-O interaction also suppresses the formation of impurity phases and reduces the adsorption strength of acidic gases such as ${\mathrm{CO}}_2$ and ${\mathrm{SO}}_2$. The lattice contraction induced by the smaller ionic radius improves thermal stability and can enhance proton diffusion in systems where proton transfer is the rate-limiting step. Furthermore, we find that Ca surface segregation can mitigate grain-boundary resistance effects. Our results demonstrate the advantages of $A$-site Ca doping in Ba-based electrolytes, clarify the mechanisms by which small-radius, high-electronegativity dopants influence proton transport and chemical stability, and provide guidance for the design of high-performance proton-conducting electrolytes.