Absorption of an isolated bulk magnetic skyrmion into an empty domain wall in a chiral ferromagnetic system is studied using the Landau-Lifshitz-Gilbert equation with and without the demagnetization effect taken into account. The full phase diagram of creation versus repulsion or annihilation is mapped out in case of both Bloch-type and Néel-type Dzyaloshinskii-Moriya interactions, with and without demagnetization. Finally, the unstable domain wall, realizable with a setup of several external magnets, contains the theoretical possibility of producing a one-dimensional version of the Kibble-Zurek mechanism, which in turn can create a number of skyrmion-antiskyrmion pairs engulfed in the domain wall: we denote them domain-wall-skyrmion–antidomain-wall-skyrmion pairs.

The chiral material BeAu was recently identified as a multiband type-I superconductor with a critical temperature of 3.2 K. As a member of the B20 crystal family (space group $P{2}_{1}3$), its band structure hosts multifold fermions at high-symmetry points, unpaired WPs, and even nodal surfaces. This renders BeAu an appealing system for investigating the interplay between superconductivity and topology. Here, we present a comprehensive first-principles analysis of BeAu's electronic structure, focusing on its Fermi surface's topology and the implications for superconductivity. Together with the presence of four- and sixfold fermions at high-symmetry points, we identify several additional isolated WPs near the Fermi level. We also determine the associated topological edge states—the surface Fermi arcs. Computing the Chern number associated to different Fermi surface sheets, we show that BeAu harbors a $\nu =4$ topological superconducting phase in the presence of $s$-wave pairing of alternating sign ($s_{\pm }$ pairing). Notably, we also identify a Fermi surface with a Chern number of $+6$; the highest value reported to date. Finally, our analysis reveals strong inhomogeneity in the orbital character of electronic states at the Fermi level, suggesting a link to the observed multigap superconductivity.

The quantum geometry of the electronic states in momentum space, distinct from real-space structural geometry, has attracted increasing interest that has advanced our understanding of quantum phenomena. An important physical manifestation is the recent discovery of anomalous Landau level spreading $\mathrm{\Delta }$ in relation to the maximal quantum distance $d$ of a singular flat band, such as that hosted in a kagome lattice. Strikingly, for a diatomic kagome lattice, we found that $\mathrm{\Delta }$ depends not only on $d$ but also $r$, the real-space diatomic distance. As $r$ increases, $\mathrm{\Delta }$ can even shrink to zero for the case of $d=1$. Interestingly, based on semiclassical theory, we derive that the dependence of $\mathrm{\Delta }$ on $r$ originates from the non-Abelian orbital magnetic moment generated by the bipartite nature of the diatomic kagome lattice with particle-hole symmetry, in analogy with the origin of electron spin from the Dirac equation. The revealed insights have broad implications in the quantum phenomena governed by the intriguing interplay of quantum and real-space geometry.

We formulate a time-dependent Fluctuating Local Field (TD-FLF) method for correlated fermion dynamics, extending the stationary FLF approach. The wave function is approximated as an ensemble of noninteracting states subject to a classical fluctuating field, with dynamics encoded in the field's time-dependent distribution. This reduces the time-dependent Schrödinger equation to a generalized eigenvalue problem in a significantly reduced basis. Applied to half-filled two-dimensional Hubbard lattices, TD-FLF yields highly accurate results, outperforming mean-field theory and capturing oscillation frequencies and amplitudes in good agreement with exact diagonalization. Its low computational cost and flexibility make TD-FLF a promising tool for simulating driven correlated systems.

The interplay between electronic modification and lattice distortion is critical for understanding emergent phenomena in correlated oxide heterostructures. For the conventional $\mathrm{LaAl}{\mathrm{O}}_3//\mathrm{SrTi}{\mathrm{O}}_3$ interface fabricated on the $\mathrm{SrTi}{\mathrm{O}}_3$ substrates, a 3% lattice mismatch dominates the interfacial lattice distortion, thereby hindering the exploration of the coupling between $\mathrm{LaAl}{\mathrm{O}}_3$ crystal structure and $\mathrm{SrTi}{\mathrm{O}}_3$ transport property. Here, when the epitaxial strain is reduced to 2% by growing the $\mathrm{LaAl}{\mathrm{O}}_3/\mathrm{SrTi}{\mathrm{O}}_3$ bilayers on the $\left(\mathrm{La},\mathrm{Sr}\right)\left(\mathrm{Al},\mathrm{Ta}\right){\mathrm{O}}_3$ substrates, the $\mathrm{LaAl}{\mathrm{O}}_3$ layers exhibit diffraction features consistent with the coexistence of two structural phases, labeled as $P_1$ and $P_2$. This structural inhomogeneity could be attributed to the competing interlayer interactions between $\mathrm{LaAl}{\mathrm{O}}_3$ and $\mathrm{SrTi}{\mathrm{O}}_3$. While the charge transfer that compensates the polar discontinuity results in the formation of oxygen vacancy in $\mathrm{LaAl}{\mathrm{O}}_3$ to expand its lattice, the interfacial redox reaction drives the oxygen migration from $\mathrm{SrTi}{\mathrm{O}}_3$ to $\mathrm{LaAl}{\mathrm{O}}_3$ with $\mathrm{LaAl}{\mathrm{O}}_3$ lattice shrinkage. Increasing the $\mathrm{LaAl}{\mathrm{O}}_3$ layer thickness reduces the lattice difference between $P_1$ and $P_2$ phases, suppressing the potential fluctuations near the conduction band minimum of $\mathrm{SrTi}{\mathrm{O}}_3$ and improving interfacial carrier mobility. Our findings provide new insights into the structural evolution at the $\mathrm{LaAl}{\mathrm{O}}_3/\mathrm{SrTi}{\mathrm{O}}_3$ interface, as well as the interlayer coupling between crystal structure and electrical transport across the correlated oxide heterostructure.

We study crossed Andreev reflection occurring in quantum dots connected to one superconducting lead and two normal leads at low temperatures $T$. Specifically, we derive an exact formula for the conductance up to order $T^2$ in the large-superconducting-gap limit, which is expressed in terms of the transmission probabilities of Cooper pairs and interacting Bogoliubov quasiparticles. Our formulation is based on the latest version of Fermi-liquid theory for the Anderson impurity model, which has clarified that the quasiparticle energy shifts of order ${\omega }^2$ and $T{}^2$—namely, corrections of the same order as those arising from the finite lifetime of quasiparticles—can be expressed exactly in terms of three-body correlations of impurity electrons. We also demonstrate how the three-body contributions evolve and affect the Cooper-pair tunneling as the Andreev level moves away from the Fermi level, using the numerical renormalization group approach. The results show that the Cooper-pair contribution to the $T{}^2$ terms of the local and nonlocal conductances becomes comparable to the Bogoliubov-quasiparticle contribution in the parameter region in which superconducting proximity effects dominate over the Kondo effect.

We propose a novel and intuitive algorithm that determines the chirality of nascent carbon caps by tracking the relative shifts of six pentagons within a topological coordinate system. Based on this algorithm, we propose three chirality mutation routes for pentagon shifts from armchair (AC) to near-AC caps, namely, the transverse shift $\left(n,n\right)\to \left(n+1,n-1\right)$, inward shift $\left(n,n\right)\to \left(n,n-1\right)$, and outward shift $\left(n,n\right)\to \left(n+1,n\right)$. Subsequently, we construct 24 representative short-capped and elongated single-walled carbon nanotubes (SWCNTs), and perform first-principles calculations to evaluate their thermodynamic stability and deformation behavior. The results reveal that dual deformation induced by both cap structure and catalyst curvature significantly influences formation and interface energies. Notably, AC and near-AC caps exhibit robust thermal stability and exceptional flexibility. This study provides a novel and rigorous mechanistic account for the prevalent synthesis of AC and near-AC SWCNTs.

Understanding how bound states in the continuum (BICs) emerge in periodic metasurfaces is essential for the controlled design of high-$Q$ resonances and their systematic manipulation. Here, we investigate the singular value decomposition (SVD) of the effective transition matrix and the scattering matrix of periodic metasurfaces within a parameter range where the metasurface sustains a BIC. Our analysis yields general and practically applicable conditions on the singular values and singular vectors that enable BIC formation. At the BIC eigenfrequency, the inverse of the largest singular value of both matrices vanishes, and the corresponding left (right) singular vector is orthogonal to outgoing (incoming) plane waves that propagate in the directions of open diffraction orders. Our SVD-based approach predicts the spectral position of the BIC and provides detailed information about its properties, including the expansion coefficients in the multipole and plane-wave bases, as well as its behavior under perturbations that transform the BIC into a quasi-BIC. The approach is numerically validated by considering both symmetry-protected and accidental BICs in arrays of scatterers supporting electromagnetic or acoustic multipole resonances. The presented SVD framework offers a broadly applicable foundation for engineering BICs and quasi-BICs in complex metasurfaces, potentially enabling new routes for wave-based devices with tailored radiative properties.

Simulating generic quantum states and dynamics is practically intractable using classical computers. However, certain special classes—namely, Clifford and matchgate circuits—permit efficient computation. They provide invaluable tools for studying many-body physics, quantum chemistry, and quantum computation. While both play foundational roles across multiple disciplines, the origins of their tractability seem disparate, and their relationship remains unclear. A deeper understanding of such tractable classes could expand their scope and enable a wide range of new applications. In this work, we make progress toward the unified understanding of the Clifford and matchgate—these two classes are, in fact, distinct special cases of a single underlying structure. Specifically, we introduce the 2D quon language, which combines Majorana worldlines with their underlying spacetime topology to diagrammatically represent quantum processes and tensor networks. In full generality, the 2D quon language is universal—capable of representing arbitrary quantum states, dynamics, or tensor networks—yet they become especially powerful in describing Clifford and matchgate classes. Each class can be efficiently characterized in a visually recognizable manner using the quon framework. This capability naturally gives rise to several families of efficiently computable tensor networks introduced in this work: punctured matchgates, hybrid Clifford-matchgate MPS, and ansatze generated from factories of tractable networks. All of these exhibit high non-Cliffordness, high nonmatchgateness, and large bipartite entanglement entropy. We discuss a range of applications of our approach, from recovering well-known results such as the Kramers-Wannier duality and the star-triangle relation of the Ising model, to enabling variational optimization with novel ansatz states.

Witnessing and tracking topological phase transitions induced by interactions with the environment is a crucial challenge. Among the various experimental approaches to detect topological properties, the Mean Chiral Displacement (MCD) has emerged as a powerful bulk probe in one-dimensional chiral systems, allowing the extraction of the topological invariant from single-particle dynamics. Here we study the dynamics of a single particle in a one-dimensional Su-Schrieffer-Heeger chain coupled to multiple cavity modes via intercell hopping terms, focusing on the out-of-equilibrium behavior of the MCD. We show that, whenever the frequency is larger than the static hopping amplitudes, the coupling induces a discontinuous jump in the MCD, already at small times, signaling that such a coupling also leaves a signature in the survival edge probability when the dynamics are initialized at one of the two edges. For frequencies comparable to the static hopping amplitudes, topological order competes with dissipative effects, which makes the MCD behave smoothly, retaining information about the driven-dissipative topology.

Fully compensated ferrimagnets possess the advantages of both collinear compensated net magnetic moments and nonrelativistic spin splitting in which the nonvolatile control is a prerequisite for realizing the spintronic nanodevices. The A-type antiferromagnetic MXene is a potential candidate for the fully compensated ferrimagnet with intralayer ferromagnetic and interlayer antiferromagnetic ordering. Based on first-principles calculations and Monte Carlo simulations, we demonstrate that the two-dimensional $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_3$ monolayer MXene is an antiferromagnetic semiconductor with a Néel temperature close to room temperature (260.2 K). By breaking symmetries between sublattices through applying an electric field or constructing ferroelectric heterostructure, we successfully tune the system into a fully compensated ferrimagnetic state, which can be detected via the magnetooptical Kerr effect. Notably, the electric-field and the nonvolatile ferroelectric control enable the promising applications of magnetic MXene in low-dimensional spintronic devices.

We present a theoretical investigation of the emergence of chiral topological superconductivity in small-angle twisted bilayer graphene (tBLG) and twisted double bilayer graphene (tDBLG). Using the low-energy continuum model and incorporating spin-triplet $p_x+i{p}_y$ pairing in each graphene layer, we construct the effective models for both tBLG and tDBLG with superconductivity. By varying the chemical potential, superconducting order parameter, and twist angle, we explore the emergence of topological superconducting phases via the calculation of Chern numbers. Our phase diagrams for tBLG and tDBLG (both AB-AB and AB-BA stackings) reveal distinct topological transitions, which are consistently marked by bulk gap-closing points. To gain further insight, we analyze the evolution of Chern numbers by tracking the number and location of gap closings within the moiré Brillouin zone. Additionally, we illustrate representative squared amplitude of Bloch states corresponding to different topological phases. In the later part of our study, the effect of trigonal warping on the topological superconducting properties is also discussed. Beyond the quantitative results, our study highlights how the interplay between moiré band structure and unconventional pairing symmetries enriches the landscape of possible superconducting states in twisted graphene systems. The framework developed here may also be extended to other multilayer moiré materials, offering a route towards engineering exotic topological superconductivity with tunable parameters.

Thermal energy and temperature govern a wide range of physical properties and dynamics in solids. X-ray diffraction can be used to monitor material-specific temperatures on ultrafast timescales and within nanostructures by exploiting thermal expansion or the Debye-Waller effect. Here, we simultaneously track the intensity and position changes of different out-of-plane Bragg peaks of a $16\text{nm}$ thick Pt film on an MgO substrate upon equilibrium heating and upon femtosecond laser excitation to quantify the mean-square atomic displacement and the lattice expansion. Our comparison of these two x-ray thermometers experimentally verifies that the in-plane expansion of homogeneously excited continuous single-crystalline thin films is forbidden on picosecond timescales. This drastically changes the out-of-plane thermal expansion coefficient, i.e., the relationship between the observed lattice expansion and the corresponding temperature increase. Thus, considering the boundary conditions of in-plane lattice expansion is generally indispensable for extracting temperatures from the lattice expansion in diffraction experiments.

We show that the Josephson diode effect becomes possible when two coupled antiferromagnetic dimers of pointlike magnetic adatoms are deposited on top of a Rashba superconductor. The degree of nonreciprocity is substantial when the arising Yu-Shiba-Rusinov (YSR) bound states approach zero energy. In this limit, these states behave as weakly coupled poor man's Majorana (PMM) excitations. This PMM regime is accompanied by highly dispersive and phase-bias asymmetric Andreev bound state dispersions. In turn, these result in a nonreciprocal Josephson current, whose diode efficiency can be controlled by varying the geometric details of the adatom's spatial configuration. In addition, thanks to spin-triplet pairing terms mixing different YSR states, the Josephson current can possess any periodicity in equilibrium, including $4\pi$. Our work opens the door to observing and harnessing Majorana behavior in currently experimentally accessible topologically trivial systems.

Flexoelectric coupling is conventionally regarded as antisymmetric, such that reversing the strain gradient reverses the polarization direction while preserving its magnitude. Here we report that this antisymmetric coupling breaks down in noncentrosymmetric single crystals driven by large strain gradients, where nonlinearity becomes operative. Harmonic-resolved measurements reveal robust even-order flexoelectric harmonics that are forbidden in antisymmetric systems, as well as the three-wave mixing indicative of symmetry breaking under dual-frequency excitation. These frequency-relevant generations provide evidence for asymmetric flexoelectricity in the nonlinear regime. A reconstructed nonlinear constitutive framework consistently accounts for all observations by incorporating even-order strain-gradient terms. Our findings establish asymmetric flexoelectricity as an intrinsic electromechanical response and uncover a symmetry-breaking mechanism in flexoelectricity.

Recent first-principles studies have shown that $\mathrm{Li}{\mathrm{B}}_2{\mathrm{C}}_2$ can reach a higher superconducting transition temperature $T_{\mathrm{c}}$ than its parent material $\mathrm{Mg}{\mathrm{B}}_2$, yet its structural instability hinders experimental realization. Here, through a systematic screening of 594 ${XM}_2{\mathrm{B}}_6{\mathrm{C}}_6$ candidate systems with different metal elements $X$ and $M$, we propose a design strategy based on isovalent metal substitution to improve structural stability while maintaining excellent superconducting performance. Using a rapid screening approach based on the zone-center electron-phonon coupling (EPC) descriptor, we screen all possible ${XM}_2{\mathrm{B}}_6{\mathrm{C}}_6$ variants derived from the $\mathrm{Li}{\mathrm{B}}_2{\mathrm{C}}_2$ network. We demonstrate that isovalent $n{s}^{1}X-M$ metal pairs, such as K-Li, Rb-Li, and Ag-Na, synergistically optimize the interlayer spacing and metal-boron/carbon hybridization to retain strong electron-phonon coupling while hardening low-frequency phonon modes to enhance lattice stability. Representative quaternary systems such as ${\mathrm{KLi}}_2{\mathrm{B}}_6{\mathrm{C}}_6, {\mathrm{RbLi}}_2{\mathrm{B}}_6{\mathrm{C}}_6$, and ${\mathrm{AgNa}}_2{\mathrm{B}}_6{\mathrm{C}}_6$ are predicted to possess $T_{\mathrm{c}}$ values significantly exceeding that of $\mathrm{Mg}{\mathrm{B}}_2$ within the same computational framework, together with enhanced stability. In contrast, aliovalent combinations (e.g., Tc-Ca) can dramatically enhance $T_{\mathrm{c}}$, but at the expense of stability. These results establish isovalent cosubstitution as a stabilization-enabled route for realizing and optimizing $\mathrm{Mg}{\mathrm{B}}_2$-like superconductivity in borocarbides by improving stability while preserving the well-known B/C σ-band-driven EPC channel.

Topological edge states typically arise at the boundaries of topologically nontrivial structures or at interfaces between regions with different topological invariants. When topological systems are extended into the nonlinear regime, linear topological edge states bifurcate into nonlinear counterparts, and topological gap solitons emerge in the bulk of the structures. Extensive studies of nonlinear topological edge states and topological gap solitons have been carried out. Following recent experimental observations in photonic systems, we leverage the strong and tunable nonlinearity of electric circuits and systematically investigate the localized states in nonlinear Su-Schrieffer-Heeger circuit lattices. Besides revisiting the nonlinear topological edge states and topological gap solitons, we uncover a new type of self-induced topological edge states which exhibit the hallmark features of linear topological edge states, including sublattice polarization, phase jumps, and decaying tails that approach zero. A distinctive feature of these states is the boundary-induced power threshold for existence. Our work unveils new opportunities for exploring novel nonlinear topological states and paves the way for the development of nonlinear topological circuits.