Bound states in the continuum (BIC) in all-dielectric metasurfaces have recently been extensively applied to enhance vibrational strong coupling in the midinfrared band due to strong field confinement and low optical loss. However, the fields of such qBIC modes are primarily confined within the structural units, hindering the effective access of molecules to electromagnetic hotspots, which significantly reduces coupling efficiency. Here, we achieved collective vibrational strong coupling between plasmonic accidental qBIC modes and molecular vibrations by embedding polymethyl methacrylate molecular layers within a metal-insulator-metal nanodisk array on a dielectric spacer. We proved the strong dependence of coupling strength on the number of molecules participating in coupling and achieved a record-breaking Rabi splitting up to 18 meV $\left(141{\mathrm{cm}}^{-1}\right)$, which is three times higher than that of reported hybrid systems with qBIC-based modes. The dramatic enhancement of Rabi splitting stems from the up to 60 times field enhancement of the plasmonic qBIC mode, as well as the perfect spatial overlap between the field hotspot and the molecular vibrations. We have also constructed a full-quantum model to quantitatively describe the coherent and incoherent coupling dynamics of the hybrid system, revealing the crucial role of the Rabi phase in the coupling spectral response and the effect of incoherent coupling strength on the vibrational polariton dynamics. The proposed hybrid system with ultrafast energy transfer and long coherence lifetime provides a platform for developing ultrafast and high-compact polariton devices in the midinfrared frequency.

Properly modeling and predicting the scattering response of a metasurface is a particularly challenging task. This has been shown to be especially difficult if the metasurface supports both local and nonlocal interactions, in the form of lattice coupling effects, multipolar contributions, or bianisotropic responses. So far, existing methods for addressing this problem often lack generality, being limited to normal incidence or applicable only to dipolar responses under oblique incidence. More general models, such as Green's function, T-matrix, or generalized susceptibility approaches, do exist; however, their application becomes challenging, particularly when analyzing the angular scattering response of complex unit cells or inhomogeneous background media. We overcome these limitations by providing a rigorous and comprehensive formalism that accommodates both oblique incidence and the presence of different superstrate and substrate. This is achieved by extending our existing metasurface modeling framework to account for nonlocal and multipolar contributions up to the any desired order and properly accounting for the scattering effects due to an inhomogeneous background medium. Additionally, our method is based on exact spherical multipole decomposition, which intrinsically accounts for toroidal contributions. We demonstrate the effectiveness of our approach by modeling the response of several dielectric and plasmonic metasurfaces that exhibit sharp spectral features including bound states in the continuum. Overall, our formalism yields excellent agreement with full-wave simulations.

Current studies of nonreciprocal superconducting (SC) transport have centered on the forward–backward asymmetry of the critical current measured along a single axis. In most realizations, this diode effect is achieved via introducing ferromagnetism or applying an external magnetic field, which drives the system into an effective Fulde–Ferrell (FF) state but often at the cost of severely suppressing the SC gap and thus compromising device robustness. Here we propose and theoretically demonstrate that coupling a conventional $s$-wave SC thin film to a $d$-wave altermagnet offers a more resilient alternative. The momentum-dependent spin splitting inherent to altermagnets induces a noncollinear SC-diode effect in the BCS state, with the critical-current anisotropy exhibiting a fourfold ($C_4$) symmetry. Upon entering the FF state at large splitting, this anisotropy gradually evolves into a unidirectional ($C_1$) pattern. Crucially, the FF pairing momentum locks to the discrete crystal axes, eliminating the rotational Goldstone mode and preserving a sizable SC gap without any abrupt or significant suppression. These combined features make the altermagnetic proximity an appealing platform to engineer symmetry-protected, energy-efficient, and programmable SC diodes for next-generation electronic devices.

We propose a Hermitian quadratic bosonic model (QBH) whose dynamical matrix exhibits distinct topological and dynamical phenomena depending on whether the hopping and pairing amplitudes are real or purely imaginary. In the real-parameter regime, the dynamical matrix is unitarily equivalent to four decoupled copies of the sublattice-symmetric non-Hermitian Su-Schrieffer-Heeger (nSSH2) model, thereby inheriting its topological phases and energy spectrum, including the Möbius phase, a gapless topological phase with fractional winding number, having no Hermitian counterpart. We show that the dynamics generated by the QBH Hamiltonian naturally reproduces non-Hermitian time evolution, without invoking nonlinear Schrödinger dynamics or ad hoc normalization. It is demonstrated by analytically calculating the Loschmidt amplitude and computing the dynamical topological order parameter under periodic boundary conditions, which displays a distinct chiral response in the Möbius phase. In contrast, when the hopping and pairing terms are taken to be purely imaginary, the dynamical matrix becomes unitarily equivalent to a different version of the sublattice-symmetric non-Hermitian Su-Schrieffer-Heeger (nSSH1) model that supports only two topological phases, trivial and nontrivial, and the Möbius phase disappears. The latter system exhibits sublattice-dependent chiral amplification under open boundary conditions. We show that this amplification arises from the nontrivial topology of the dynamical matrix, establishing a clear link between topological phase and amplification behavior in the imaginary-parameter regime.

Light carrying orbital angular momentum (OAM)—known as vortex beams—has broadened the scope of understanding and applications of light's angular momentum. Optical tweezers using OAM, often referred to as optical spanners, have significantly expanded the tunability of optical manipulation. A key frontier now lies in understanding how vortex beams interact with quantum states of matter. In this work, we numerically investigate the dynamics of a superconductor under vortex beam illumination and demonstrate the transfer of angular momentum from light to the superconducting collective mode, resulting in mechanical rotation. Our findings open a pathway for optical manipulation in the quantum regime, which we term the quantum optical spanner.

Time-reversal symmetry breaking is generally understood to be detrimental for superconductivity. However, recent experiments found superconductivity emerging out of a normal state showing a finite anomalous Hall effect, indicative of time-reversal symmetry breaking, in diverse systems from kagome metals, $1T^{\prime }\text{−}{\mathrm{WS}}_2$, to twisted ${\mathrm{MoTe}}_2$ and rhombohedral graphene. Motivated by these findings, we ask how such an anomalous Hall state affects different pairing symmetries and whether it necessarily implies unconventional pairing. To this end, we study the stability of superconducting orders and the mechanisms that suppress superconductivity in the prototypical anomalous Hall system, the Haldane model, where complex hopping parameters result in loop-current order with a compensated flux pattern. We find that neither spin-singlet nor spin-triplet states are generically suppressed, but the real-space sublattice structure plays a crucial role in the stability of the orders. Interestingly, the nearest-neighbor chiral states of $d\pm id$ or $p\pm ip$ symmetry couple linearly to the flux, such that the two otherwise degenerate chiralities split under finite flux. As an experimental probe to distinguish the various orders in this system, we study the anomalous thermal Hall effect, ${\kappa }_{xy}/T$, which vanishes at zero temperature for topologically trivial superconducting states, but reaches a finite value corresponding to the Chern number in a topologically nontrivial superconducting state. Our results illustrate that broken time-reversal symmetry through a finite flux is neither generically destructive for superconductivity nor does it imply nontrivial topological order of the emerging superconducting state. However, in the case of multiple competing pairing channels, the loop-current order can favor a chiral superconducting state.

The quantum Fisher information, the quantum analog of the classical Fisher information, is a central quantity in quantum metrology and quantum sensing due to its connection to parameter estimation and fidelity susceptibility. Using numerically exact methods applied to a paradigmatic open quantum system, the spin-boson model, we calculate both static and dynamical quantum Fisher information matrix elements with respect to spin-bath couplings and magnetic field strengths. As the spin-bath interaction increases, we first show that the coupling-coupling matrix elements relative to the ground state of the Hamiltonian are linked to the entanglement growth and signal the Berezinskii-Kosterlitz-Thouless quantum phase transition through their nonmonotonic behavior. We also point out that the static quantum Fisher information exhibits a nonperturbative behavior in the zero-coupling limit, which we justify with an analytic argument. Furthermore, we demonstrate that the time-dependent matrix elements can reveal non-Markovian effects as well as the transition from the coherent to incoherent regime at the Toulouse point, remaining robust under pure dephasing noise. Nonmonotonic signatures of the quantum Fisher information matrix reflect changes in quantum resources such as entanglement and coherence, quantify non-Markovian behavior, and enable criticality-enhanced quantum sensing, thereby shedding light on key features of open quantum systems.

Noncollinear antiferromagnets (NCAFs) have recently emerged as promising candidates for future spintronic technologies, offering ultrafast switching, negligible stray fields allowing dense packing, and robustness against external magnetic perturbations. When interfaced with ferromagnets (FMs), they can strongly influence interfacial exchange and spin-torque mechanisms that enable manipulating magnetic order and realizing functionalities beyond conventional heavy metals (HMs) based FM/HM heterostructures. Here, we perform a broadband ferromagnetic resonance (FMR) study to systematically investigate the magnetization dynamics and spin-to-charge conversion in permalloy (Py) and ${\mathrm{Mn}}_3\mathrm{Pt}$ bilayers. High-quality Py films provide well-defined FMR spectra with a low Gilbert damping parameter (${\alpha }_{\mathrm{eff}}\approx 9.8\times {10}^{-3}$). We observe a pronounced enhancement of damping with intrinsic value ${\alpha }_{\mathrm{int}}\approx 3.1\times {10}^{-2}$ in the $\mathrm{Py}/{\mathrm{Mn}}_3\mathrm{Pt}$ bilayer, indicating efficient spin pumping into the NCAF layer. Frequency dependent linewidth analysis shows a predominantly Gilbert type damping in the bilayers and the corresponding effective spin-mixing conductance ($g_{\mathrm{eff}}^{\uparrow \downarrow }\approx 4.8\times {10}^{18}{\mathrm{m}}^{-2}$) is comparable to that of other high-performance antiferromagnetic heterostructures. These results are significant for establishing NCAFs as a candidate material for spin generation and highlight the potential of $\mathrm{Py}/{\mathrm{Mn}}_3\mathrm{Pt}$ bilayers for efficient and ultrafast spintronic applications.

Within the Bogoliubov–de Gennes equations formalism, we study subgap quasiparticle states in a helical magnetic atom chain placed on top of a three-dimensional superconductor. The surface of the superconductor is modeled as an impenetrable barrier for electrons. As a result, for a surface impurity, spherically symmetric scattering is suppressed, and we consider scattering with angular momentum $l=1$. For a single impurity, we find that the density of states near the surface corresponding to a Yu-Shiba-Rusinov state falls off proportionally to the distance from the impurity to the minus fourth power, opposed to the inverse-square falloff law characteristic for an impurity in the bulk, which is typically used for interpretation of scanning tunneling microscopy experiments. For a helical atom chain, we calculate the band spectrum of hybridized Yu-Shiba-Rusinov states and the Majorana number and analyze the structure of Majorana edge modes. In the limit of large coherence lengths, the Majorana wave function in the chain falls off proportionally to the inverse square of the distance from the edge of chain, which is faster than for a magnetic chain in the bulk of a superconductor. The energy of the corresponding edge mode is proportional to the inverse square of the length of the chain. When the the atomic spins form a planar helix, the system belongs to the Altland-Zirnbauer symmetry class BDI. By calculating the corresponding topological invariant we demonstrate that in this case one edge of the chain can host up to three Majorana modes.

We use the numerically unbiased determinant quantum Monte Carlo method to systematically investigate the three-orbital Emery model in the normal state in a wide range of local interactions, charge transfer energy, and doping levels. We focus on the influence of the on-site Hubbard $U_{dd}$ and the charge transfer energy scale ${\epsilon }_p$ on the electronic properties via the orbital occupancies, local moments, spin correlations, and spectral properties. Rich features of the orbital-resolved local and momentum-dependent spectra are revealed to be associated with the possible Zhang-Rice singlet breakdown reflected by the peak splitting near the Fermi level in the heavily overdoped regime. Moreover, the pseudogap features at a small charge transfer energy scale (relevant to cuprates) are shown to diminish at larger ${\epsilon }_p$, which implies the weakening or absence of the pseudogap in the infinite-layer nickelates. Besides, an optimal value of ${\epsilon }_p$ is identified for maximizing the antiferromagnetic spin correlations. Our large-scale simulations provide additional insights into the well-established Emery model, particularly in the regime of heavily overdoped and/or large charge transfer energy scale.

Hopf insulators represent an exceptional class of topological matter, unanticipated by the periodic table of topological invariants. These systems point to the existence of previously unexplored states of matter with unconventional topology. In this work, we take a step toward exploring this direction by investigating correlation-driven instabilities of Hopf insulators. Organizing our analysis around the topological quantum critical point that separates the Hopf insulating phase from a trivial insulator, we demonstrate the emergence of unconventional Weyl semimetallic and topological insulating states. Notably, upon doping, the Weyl semimetal supports nonreciprocal superconductivity and a Bogoliubov-Fermi surface, potentially providing a novel framework for realizing the superconducting diode effect. Finally, we highlight the interconnectedness of the effective descriptions of correlated Hopf insulators, two-dimensional quadratic band-touching semimetals, and Luttinger semimetals.

We study charge and spin transport across a junction between an altermagnet (AM) and a $p$-wave magnet (PM) using a continuum model with boundary conditions tailored to the spin-split band structures of the two materials. Remarkably, although neither AM nor PM is spin-polarized, we find that the junction supports finite spin currents both longitudinally and transversely. We compute the longitudinal and transverse charge and spin conductivities as functions of the crystallographic orientations and the relative angle between the Néel vectors of the AM and PM. Our results reveal that transverse charge and spin conductivities can be finite even when the longitudinal charge conductivity vanishes. For suitable parameter choices and orientation angles, the transverse conductivities are more prominent than the longitudinal ones. The origin of these effects lies in the matching and mismatching of transverse momentum modes ($k_y$) across the junction combined with the spin-dependent band splitting in the AM and PM. Furthermore, while the transverse charge conductivity may be zero for certain orientations, the transverse spin conductivity remains finite due to unequal contributions of opposite $k_y$ channels. These findings highlight AM-PM junctions as a promising platform for tunable generation and control of transverse charge and spin currents driven purely by crystallographic orientation and spin structure.

The Drude weight (DW) is an essential quantity that characterizes the quantum transport properties of many-body systems. However, a rigorous understanding and exact computation of DWs, particularly for strongly correlated systems with doping, still remain elusive. In this article, taking advantage of the quantum integrability, we calculate exactly the DWs and Seebeck effect for generic filling factor in one-dimensional Fermi-Hubbard model with arbitrary interaction strengths and magnetic fields. We build up its intrinsic connection to the Luttinger parameters and derive universal scaling laws for DWs across phase transitions. Our results provide a deep understanding of mutual influences in transport between the spin and the charge degrees of freedom, showing a counterintuitive subtle spin-charge coupling effect and uncovering the microscopic origin of the (spin) Seebeck effects in thermal conductivity. Finally, we propose an experimental protocol to measure the DWs in ultracold atomic systems.

We investigate interacting Su-Schrieffer-Heeger (SSH) chains with two- and three-site unit cells using density matrix renormalization group (DMRG) simulations. By selecting appropriate filling fractions and sweeping across interaction strength $J_z$ and dimerization $\delta$, we map out their phase diagrams and identify transition lines via entanglement entropy and magnetization measurements. In the two-site model, we observe the emergence of an interaction-induced antiferromagnetic intermediate phase between the topologically trivial and nontrivial regimes, as well as a critical region at negative $J_z$ with suppressed magnetization and finite-size scaling of entanglement entropy. In contrast, the three-site model lacks an intermediate phase and exhibits asymmetric edge localization and antiferromagnetic ordering in both positive and negative $J_z$ regimes. We further examine the response of edge states to Ising perturbations. In the two-site model, zero-energy edge modes are topologically protected and remain robust up to a finite interaction strength. However, in the three-site model, where the edge states reside at finite energy, this protection breaks down. Despite this, the edge-localized nature of these states survives in the form of polarized modes whose spatial profiles reflect the noninteracting limit.

We study the entanglement and bipartite fluctuations of fractonic phases in a one-dimensional dipole-conserving Bose-Hubbard chain using the density matrix renormalization group method. We demonstrate that bipartite charge fluctuations fail to detect quantum phase transitions in fractonic systems. Instead, we introduce bipartite dipole fluctuations, ${\mathcal{F}}^d$, which exhibit scaling laws identical to the entanglement entropy $S$. For example, at integer filling $n=2$, both ${\mathcal{F}}^d$ and $S$ show logarithmic scaling in dipole Luttinger liquids and area-law scaling in dipole Mott insulators. Interestingly, in the dipole supersolid phase at noninteger filling $n=3/2$, we reveal that ${\mathcal{F}}^d$ and $S$ obey area laws despite the phase being compressible and hosting long-range dipole-dipole order. Moreover, we identify another phase at $n=3/2$, previously called the fractional Mott insulator phase, as a dipole-conserving charge density wave state. In this phase, ${\mathcal{F}}^d$ and $S$ follow area laws, but ${\mathcal{F}}^d$ exhibits an additional period-2 oscillation. These findings provide insights into the interplay between dipole conservation, quantum fluctuations, and entanglement in the fractonic phases.

The negatively charged boron vacancy center in two-dimensional (2D) hexagonal boron nitride has emerged as a promising quantum sensor. However, its sensitivity is constrained due to ubiquitous nuclear spins in the environment. The nuclear spins, hyperfine coupled with the central electron spin, effectively behave as magnetic field fluctuators, leading to rapid decoherence. Here, we explore the effectiveness of static magnetic field strength and orientation in realizing peculiar subspaces that can lead to enhanced spin coherence. Specifically, using detailed numerical simulations of the spin Hamiltonian, we identify specific field configurations that minimize energy gradients and, consequently, are expected to facilitate decoherence suppression. We also develop an approximate analytical model based on the perturbation theory that accurately predicts these low-gradient subspaces for magnetic fields aligned with the electron spin quantization axis, applicable not only to boron vacancies but to any spin-1 electronic system coupled to nearby nuclear spins. Furthermore, to stimulate experimental validation, we estimate coherence lifetimes as a function of various bias field configurations and demonstrate that significant decoherence suppression can indeed be achieved in certain regions. These findings and the developed methodology offer valuable insights for mitigating decoherence in a low-field regime.