The momentum dependence of Rashba spin-orbit coupling (RSOC) is a key ingredient for engineering topological superconductors (TSCs), yet research has overwhelmingly focused on its linear-in-momentum form. This focus has restricted time-reversal invariant TSCs to helical $p$-wave states, which are characterized by a ${\mathbb{Z}}_2$ topological invariant that permits at most a single Majorana Kramers pair at a given boundary. Their existence has also been tied to the stringent criterion of an odd number of Fermi surfaces (FSs). In this work, we establish higher-order RSOC as a powerful design principle to go beyond the ${\mathbb{Z}}_2$ classification and the odd-FS criterion. We demonstrate that a bilayer system with a pure cubic RSOC and an intrinsic odd-parity pairing on a single FS yields a rare 2D helical $f$ wave TSC. This state is characterized by a large mirror Chern number (MCN) of ${\mathcal{N}}_{\text{M}}=3$ and hosts three Kramers pairs of Majorana edge modes. Remarkably, the interplay of linear and cubic RSOCs in this bilayer can generate a helical hybrid $p+f$-wave TSC with an even larger MCN of ${\mathcal{N}}_{\text{M}}=4$ from a normal state with two FSs, thereby circumventing the conventional odd-FS criterion. Our work establishes higher-order RSOC as a “topology multiplier” for realizing TSCs with multiple Majorana Kramers channels, fundamentally reshapes the criteria for helical TSCs, and holds immediate relevance for tunable platforms like oxide heterostructures.

The coexistence of topological magnons and electrons in magnetic materials presents a compelling route toward developing low-dissipation, multifunctional spintronic devices. However, material systems enabling their simultaneous realization and control remain largely unexplored. Here, we propose the coexistence and concurrent tunability of magnonic and electronic Chern insulator phases in Kitaev magnets and use ${\mathrm{MnBr}}_3$ monolayer as a prototype. We find the significant Kitaev interaction in ${\mathrm{MnBr}}_3$ induces the magnonic Chern insulator phase, manifesting as the magnon thermal Hall effect. Concurrently, ${\mathrm{MnBr}}_3$ exhibits the quantum anomalous Hall effect driven by its electronic Chern insulator phase. Crucially, we demonstrate that these dual topological phases can be simultaneously controlled by reorienting the in-plane spins with an external magnetic field. Our findings not only deepen the fundamental understanding of spin excitations in Kitaev magnets but also provide a promising platform for exploring the interplay between electronic and magnonic topology.

Nonvolatile manipulation of magnetic orderings in two-dimensional (2D) van der Waals (vdW) materials presents a promising avenue for advanced spintronic applications. Bilayer ${\mathrm{CrI}}_3$ (BL-${\mathrm{CrI}}_3$) exhibits an interlayer antiferromagnetic (AFM) ground state, distinct from the interlayer ferromagnetic (FM) ordering of its bulk counterpart, making it a compelling system for studying the magnetic phase transition. While integrating BL-${\mathrm{CrI}}_3$ with a ferroelectric layer like $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ has been proposed as a strategy to modulate these transitions, prior computational studies have yielded conflicting results. Here, we systematically investigate BL-${\mathrm{CrI}}_3/\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ heterostructures using first-principles calculations, examining the effects of lattice strain, spin-orbit coupling (SOC), and electric polarization on magnetic stability. Our findings reveal that larger in-plane lattice constants favor the AFM state, while SOC promotes FM ordering. Notably, a bilayer ${\mathrm{In}}_2{\mathrm{Se}}_3$ substrate proves highly effective in achieving nonvolatile magnetic ground-state reversal. These results decipher the critical roles of strain, SOC and electric polarization in the manipulation of magnetism in 2D materials and provide essential insights for designing 2D vdW heterostructures with robust magnetoelectric properties.

The miniaturization of superconducting electronics demands precise control over quasiparticle dynamics at the nanoscale. Understanding and controlling quasiparticle dynamics is essential for advancing superconducting electronics, particularly as device dimensions approach the nanoscale. Here we present direct experimental evidence for the quasiparticle-to-supercurrent conversion in planar SN-N-NS Josephson nanobridges with submicron electrodes. By employing a versatile measurement platform, we demonstrate that the geometry of injection through superconducting or normal-metal leads significantly alters the critical current and junction resistance. Using a tunable measurement setup that allows current injection through either superconducting or normal-metal leads, we uncover marked changes in critical current and resistance depending on the injection geometry. These effects become significant when electrode widths fall below the characteristic conversion length of $\sim 400\mathrm{nm}$. These observations are quantitatively explained by a phenomenological model that accounts for nonequilibrium transport and incomplete quasiparticle conversion in narrow electrodes. These results point to the emergence of nonequilibrium transport governed by an intrinsic conversion length. We develop and apply a method for extracting this length from standard transport measurements, offering a practical diagnostic for nanoscale superconducting circuits. Our work establishes fundamental design rules for minimizing energy dissipation and optimizing performance in superconducting quantum devices. Our findings enable optimized design of compact Josephson junctions and support the integration of proximity-based weak links into scalable superconducting logic and sensing architectures.

Josephson diode (JD) effect in Josephson tunnel junctions (JTJs) has attracted a great deal of attention due to its importance for developing superconducting-circuitry-based quantum technologies. Even though the preparation of high-quality JTJs by techniques employed in the semiconductor industry has been demonstrated, which was an important milestone because JTJs are the building blocks of superconducting electronics even before the quantum era, the JD effect has not been accomplished in them, nor has the highly desirable electrical control of the effect. We report here the fabrication of JTJs featuring a composite tunnel barrier of ${\mathrm{Al}}_2{\mathrm{O}}_3$ and ${\mathrm{Hf}}_{0.8}{\mathrm{Zr}}_{0.2}{\mathrm{O}}_2$ using complementary-metal-oxide-semiconductor compatible atomic layer deposition. These JTJs were found to show the JD effect in nominally zero magnetic fields with nonreciprocity controllable via an electric training current, yielding a surprisingly large diode efficiency. The quasiparticle tunneling, through which the Josephson coupling in a JTJ is established, was found to show theoretically expected gap features but no nonreciprocity. We attribute these observations to the simultaneous presence of positive and negative local Josephson couplings in the JTJs, with the negative Josephson coupling originating from indirect tunneling, which results in spontaneous time-reversal symmetry breaking. The double-minima washboard potential for the ensemble-averaged phase difference in the resistively and capacitively shunted junction model is shown to fully account for the experimentally observed JD effect.

${\mathrm{Ni}}_3{\mathrm{TeO}}_6$ is a polar magnet with a pronounced magnetoelectric (ME) effect under high magnetic fields ($\approx 9\mathrm{T}$). Substitution of Ni with Co in ${\mathrm{Ni}}_3{\mathrm{TeO}}_6$ modulates the magnetic structure and reduces the critical field required to induce the ME response. In this study, we have grown single crystals of ${\mathrm{NiCo}}_2{\mathrm{TeO}}_6$ and measured the magnetic, dielectric, and magnetostriction properties. In addition, the temperature- and magnetic-field dependence of the dynamic ME coefficient (${\alpha }_{\mathrm{E}}=\mathrm{d}E/\mathrm{d}H$) was measured, enabling the construction of comprehensive ME phase diagrams. Pronounced peaks and dips in ${\alpha }_{\mathrm{E}}$ are observed at magnetic phase boundaries induced by temperature or magnetic field. Notably, the maximum ${\alpha }_{\mathrm{E}}$ is observed near the vicinity of the Néel temperature ($T_{\mathrm{N}}$) at a low magnetic field ($\approx 1.5\mathrm{T}$), in stark contrast with the high-field requirement in parent ${\mathrm{Ni}}_3{\mathrm{TeO}}_6$. Combined analysis of ${\alpha }_{\mathrm{E}}$ and magnetostriction data reveals that the anisotropic ME effect arises from the coexistence of spin-induced and magnetostriction-mediated polarization changes. These findings elucidate the intricate interplay among spin order, lattice strain, and electric polarization in ${\mathrm{NiCo}}_2{\mathrm{TeO}}_6$. Moreover, the combination of the dynamic ME coefficient and magnetostriction measurements provides a robust experimental framework for disentangling the microscopic origins of the ME effects.

Ab initio molecular dynamics (AIMD) refers to the solution of Newton's equations of motion for ions with forces ${\mathbf{f}}_i=-\partial E/\partial {\mathbf{R}}_i$ calculated from self-consistent electronic structure calculations. So-called machine-learning force field (ML-FF) schemes parametrize the potential energy surface very efficiently and make it possible to extend the time scale of AIMD simulations by orders of magnitude. The Landau-Lifshitz equation describes the dynamics of atomic magnetic moments ${\mathbf{m}}_i$ in effective fields ${\mathbf{h}}_i=-\partial E/\partial {\mathbf{m}}_i$ which in addition to containing external magnetic fields, describe contributions from interatomic exchange interactions, long-range dipolar interactions, anisotropy fields, etc. In this publication, we add the magnetic degrees of freedom to the widely used Gaussian approximation potential of machine learning and present a model that describes the potential energy surface of a crystal based on atomic coordinates and noncollinear magnetic moments. Incorporating the translational, rotational, inversion, and permutational symmetries of magnetic interactions, the ML model can describe various magnetic interactions expanded into two-body, three-body terms, etc., in the spirit of the atomic cluster expansion. Assuming an adiabatic approximation for the spin directions, the ML model depends solely on the positions and orientations of atomic spins and is computationally efficient enough to make coupled ab initio molecular and spin dynamics possible. To illustrate the ML model, we implement a two-body form for the interatomic exchange interaction. Comparing the total energies and local exchange fields predicted by the model for noncollinear spin arrangements with the results of constrained noncollinear density functional calculations for bcc Fe yields very good results, with agreement on the level of 1 meV/spin for the total energy.

Transport properties of single- and two-site mesoscopic quantum Hall (QH) circuits at high transparencies can be described in terms of the lowest-order backscattering processes, enabling a mapping to the boundary sine-Gordon model. We show that this description breaks down in circuits with four or more sites, where higher-order backscattering processes become relevant and qualitatively modify the low-energy physics, while remaining exactly marginal in three-site geometries. Focusing on the four-site circuit, we derive an effective low-energy theory that captures the resulting interaction-driven physics and reveals the emergence of unique quantum critical points. In the vicinity of these critical points, we obtain universal conductance and scaling behavior and establish the robustness of the associated non-Fermi liquid physics. We further introduce tunneling in multichannel multisite QH circuits and propose a promising route for realizing diverse quantum critical phenomena. We show that a boundary sine-Gordon description can be restored in multichannel multisite QH circuits by appropriately looping selected edge channels, a procedure that is experimentally feasible. Finally, we analyze the nonequilibrium heating effects relevant to transport measurements in QH circuits. Altogether, our results establish multisite QH circuits as a versatile and highly controllable platform for simulating interaction-driven quantum critical phenomena.

The two-dimensional (2D) materials with coexistence of Dirac points and Van Hove singularities (VHSs) provide a promising platform for seeking topological superconductivity or ferromagnetism at high critical temperatures. However, ideal examples combining electronic topological properties with superconductivity or ferromagnetism are scarce. Here, through structural search, we identify 2D ${\mathrm{Sc}\mathit{X}\mathrm{S}}_2$ ($X$ = Rh, Ta, Mo) monolayers with simple square or rectangular lattices, where VHSs lie near Dirac points close to the Fermi levels. Using first-principles calculations, Bardeen-Cooper-Schrieffer theory, and Monte Carlo simulations, we found that all the three monolayers exhibit nontrivial topological electronic properties. Moreover, ${\mathrm{ScRhS}}_2$ is intrinsically superconducting with Tc = 1.36 K; ${\mathrm{ScTaS}}_2$ shows tunable superconductivity reaching Tc = 2.21 K under 6% uniaxial tensile strain which also displays ferroelasticity induced by the Jahn-Teller effect; and ${\mathrm{ScMoS}}_2$ hosts a topological ferromagnetic half-metal ground state with a giant anomalous Hall effect and Curie temperature of 329 K stabilized by a high magnetic anisotropy energy of 1.837 meV/Mo. These results establish ${\mathrm{Sc}\mathit{X}\mathrm{S}}_2$ monolayers as a versatile 2D material family for exploring exotic mixtures of topological states, superconductivity, and half-metal ferromagnetism, offering potential for novel electronic and spintronic applications.

We develop a microscopic theory of the trion polaron: a bound state of two electrons and one hole, dressed by longitudinal optical (LO) phonons. Starting from the Fröhlich Hamiltonian, which describes the interaction of charged particles with LO phonons in three-dimensional (bulk) and two-dimensional (monolayer) polar crystals, we adopt the intermediate-coupling variational approximation of Lee, Low, and Pines, and generalize it for the three-body problem. This yields an effective three‐particle Hamiltonian with renormalized electron-electron and electron-hole interactions, similar to those obtained for exciton polaron and bipolaron problems. We compute the binding energies for a family of bulk perovskite materials and several atomic monolayer materials characterized by pronounced polar effects, providing quantitative benchmarks for spectroscopic measurements.

Topology and nonlinearity are deeply connected. However, whether topological effects can arise solely from the structure of nonlinear interaction terms, and the nature of the resulting topological phases, remain to large extent open questions. Here we consider a chain of parametrically driven quantum resonators coupled only via weak nearest-neighbor cross-Kerr interaction, without any quadratic tunneling term. We show that, when the drive overcomes a critical threshold value, the system undergoes a transition from the atomic limit of decoupled oscillators to a symmetry-broken topological phase. The topology is determined by the interplay of local and nearest-neighbor Kerr nonlinearities, yielding a nontrivial bulk-boundary correspondence. In the topological phase, we derive analytical approximations for the low-energy spectrum, identifying the conditions to observe topological edge modes.

Understanding thermal properties of materials is fundamental to technological applications and to discovering new phenomena. In particular, advances in experimental techniques such as cold-atom measurements allow the simulation of paradigmatic Hamiltonians with great control over model parameters, such as the Hubbard model. One aspect of this model which is not much explored is the behavior of the specific heat as a function of density. In this work, we perform determinant quantum Monte Carlo simulations of the Hubbard model interpolating between the square and triangular lattices to analyze the specific heat as the filling, interaction, and temperature of the system are changed. We found that, with strong correlations, the specific heat presents a three-maxima structure as a function of filling, with local minima between them. This effect can be explained by a decomposition of kinetic and potential contributions to the specific heat, demonstrating interesting phenomena away from the commonly studied half-filling regime. Moreover, by analyzing the kinetic contribution in momentum space we show that, connected to this specific heat behavior, there is a density anomaly detected through the thermal expansion coefficient. These momentum-space quantities are accessible using cold-atom experimental measurements at multiple temperatures. Finally, we map the location of these phenomena and connect the thermal expansion anomaly with the well-known Seebeck coefficient change of sign. Our results provide an alternative perspective to analyze this change of sign.

Kagome metals provide a material platform for probing new correlated quantum phenomena due to the naturally incorporated linear dispersions, flat bands, and Van Hove singularities in their electronic structures. Among these quantum phenomena is the charge density wave (CDW), or the distortion of the lattice structure due to the motion of correlated electrons through the material. CDWs lower the energy of the compound, creating an energy gap that facilitates behaviors akin to superconductivity, nonlinear transport, or other quantum correlated phenomena. The kagome metal FeGe has been shown to host a CDW transition at approximately 100 K, and its occurrence is strongly influenced by the sample annealing conditions. However, a notable gap in the literature is the lack of clear thermoelectric transport evidence for electronic structure changes associated with this CDW transition. Here, we present evidence of electron behavior modification due to annealing disorder via thermoelectric measurements on FeGe crystals presenting a CDW transition and those without a CDW. The observed Nernst effect and Seebeck effects demonstrate pronounced modifications of electrical transport properties associated with CDW formation and its suppression by annealing-induced disorder, including a change in the thermopower sign and a strong enhancement of the Nernst response in the CDW state. Our results provide evidence of multiple phase transitions, which confirms the influence of CDW on the thermal properties of FeGe and demonstrates the suppression of CDW with sufficient disordering.

We investigate the microwave absorption spectra of a split-ring resonator (SRR) based on a high-mobility two-dimensional electron system (2DES) in an AlGaAs/GaAs heterostructure. Introducing a split into the ring-shaped mesa gives rise to an additional plasmon resonance exhibiting strong polarization dependence. The frequency of the split-induced mode displays a negative magnetic-field dependence, while its dispersion is characteristic of one-dimensional plasma excitations. We also address the tunability of the plasmon resonances in the SRR-shaped 2DES.

Topological thermal transport offers a quantum route to regulate heat flow through Berry-curvature-driven responses. However, approaches for dynamically switchable control of such transport are lacking. Here, we propose an interlayer-sliding-driven dynamical evolution mechanism to control topological thermal transport in bilayer antiferromagnetic electron crystals, exemplified by ${\mathrm{ScI}}_2$. Sliding breaks spin group symmetry, generates ferroelectric polarization, and reshapes layer-resolved Berry curvature, resulting in strong modulation of anomalous Nernst and thermal Hall conductivities as signatures of topological phase transitions. Giant thermal Hall peaks and Hall plateaus emerge under sliding, demonstrating amplified topological heat transport response. Reversing the sliding direction switches spin splitting and transport polarity, enabling direct reading of stacking order and motion direction. Our work uncovers topological thermoelectric characteristics and superior transport performance in sliding systems, providing new insights for thermoelectric device design and applications.

We report a gate-tunable magnetoresistance and nonlinear Hall effect in thin ${\mathrm{Bi}}_y{\mathrm{Sb}}_{2-y}{\mathrm{Te}}_{3-x}{\mathrm{Se}}_x$ films grown by molecular beam epitaxy. The Hall coefficient $R_H$ exhibits distinct nonlinear behavior controlled by the gate voltage: a $\sim 2\%-3\%$ increase at low field ($B\sim 0.5\mathrm{T}$), opposite slopes for positive and negative gate biases at higher fields, and a substantial change at large negative gate voltages ($\sim -90\mathrm{V}$). Joint analysis of the gate dependences of magnetoresistance and the nonlinear Hall effect demonstrates a combined effect of topological surface states, trivial bulk states, holes in the inversion layer, and the smooth energy disorder, when the Fermi level is near the Dirac point. Because of the existence of several carrier groups, quantum corrections to the conductivity manifest themselves not only in the magnetoresistance, but also in the Hall effect. Our model quantitatively reproduces the gate dependence of both longitudinal and Hall resistances, allowing us to determine the concentrations and mobilities of all contributing carrier types.

Cavity optomechanical systems enable coherent photon-phonon interactions essential for quantum technologies, yet high-performance devices have been limited to suspended structures. Here, we overcome this limitation by demonstrating cavity Brillouin optomechanics in a suspension-free racetrack microring resonator on a lithium-niobate-on-sapphire chip, a platform that merits high stability and scalability. We demonstrate coherent coupling between telecom-band optical modes and a 9.6 GHz phonon mode, achieving a maximum cooperativity of 0.41 and a phonon quality-factor-frequency product of ${10}^{13}\mathrm{Hz}$. The momentum-matching condition inherent to traveling-wave Brillouin interactions establishes a one-to-one mapping between the optical wavelength and phonon frequency, enabling multichannel parallel operations across nearly $300\mathrm{MHz}$ in phonon frequency and $40\mathrm{nm}$ in optical wavelength. Our suspension-free architecture provides a coherent photon-phonon interface compatible with wafer-scale integration, opening pathways toward hybrid quantum circuits that unite photonic, phononic, and superconducting components on a single chip.

The Wang-Teter (WT)-like nonlocal kinetic energy density functional (KEDF) in the framework of orbital-free density functional theory, while successful in some bulk systems, exhibits a critical Blanc-Cancès instability [J. Chem. Phys. 122, 214106 (2005)] when applied to isolated systems, where the total energy becomes unbounded from below. We trace this instability to the use of an ill-defined average charge density, which causes the functional to simultaneously violate the scaling law and the positivity of the Pauli energy. By rigorously constructing a density-functional-dependent kernel, we resolve these pathologies while preserving the formal exactness of the original framework. By systematically benchmarking single-atom systems of 56 elements, we find the resulting KEDF retains computational efficiency while achieving an order-of-magnitude accuracy enhancement over the WT KEDF. In addition, this proposed KEDF preserves WT's superior accuracy in bulk metals, outperforming the semilocal functionals in both regimes.