In recent years, nonlinear transport phenomena have garnered significant interest in both theoretical explorations and experiments. In this work, we utilize the semiclassical wave-packet theory to calculate disorder-induced second-order transport coefficients: second-order electrical ($\sigma$), thermoelectric ($\alpha$), and thermal ($\kappa$) coefficients, capturing the interplay between side-jump and skew-scattering contributions in systems with time-reversal symmetry. By employing a realistic model of topological insulators specifically tailored to represent ${\text{Bi}}_2{(\text{Se},\text{Te})}_3$ materials, we quantitatively characterize the Fermi-level dependence of these second-order transport coefficients by explicitly including Coulomb impurity potentials. Furthermore, we elucidate the relationships between these coefficients, establishing the second-order Mott relation and the Wiedemann-Franz law induced by disorder. This study develops a comprehensive theoretical framework elucidating the nonlinear thermoelectric transport mechanisms in quantum material systems.

Rydberg atom arrays composed of multiple atomic species stand as a highly promising platform for quantum computation. However, the underlying physics of these systems as quantum many-body systems remains poorly understood, owing to the intricate competition between attractive and repulsive interactions, phenomena that entirely defy the Rydberg blockade mechanism. We systematically calculate the ground state phase diagram of alternating two-species atom arrays and their quench dynamics. Our findings reveal several novel quantum states absent in traditional cold-atom platforms, such as the period-4 product state $|1100...\rangle$, the period-6 product state $|111000...\rangle$, and an order-disorder mixed phase. In the quench dynamics, we confirm that the ${\mathbb{Z}}_2$ ordered states qualify as novel quantum many-body scars. Based on our perturbation analysis, the underlying physics ought to be described by a series of Cooper pair states spanning the entire energy spectrum, rather than the PXP low-energy effective model. A detailed analysis is also provided regarding the experimental preparation of those product states. Numerical evidence demonstrates that the proposed scheme exhibits robustness against typical experimental imperfections, thereby confirming its experimental feasibility. Moreover, the ground state problem of the two-species array naturally maps to more general combinatorial optimization problems, extending the class of optimization tasks accessible to programmable neutral-atom quantum processors. Our work paves a new way for quantum simulation of novel quantum many-body states, which emerge from the interplay between competing interactions among different atom species and quantum fluctuations.

We show that the low-energy theory of a $d$-wave altermagnet is characterized by anisotropic Dirac cones with spin-split band structures based on a recently proposed tight-binding model. In this system, spin-selective perfect elliptic dichroism emerges, enabling exclusive excitation of either up-spin or down-spin electrons by tuning the ellipticity of the incident light. We further derive a formula for the third-order photocurrent generated under simultaneous application of elliptically polarized light and a static electric field, expressed in terms of the quantum metric and Berry curvature. Using this formula, we demonstrate that only an up-spin polarized current is induced. This third-order response constitutes the leading photocurrent, as second-order processes such as injection and shift currents are forbidden by the inversion symmetry inherent to altermagnets. They lead to the prediction that, in insulating $d$-wave altermagnets, a spin-polarized third-order photocurrent arises as the leading electric response when elliptically polarized light and a static electric field are applied simultaneously. These findings provide a foundation for future developments in photoinduced spintronics based on altermagnets.

Topological Weyl semimetals typically feature twofold degenerate points of bulk bands, which can be classified by four distinct topological charges, i.e., charge 1, 2, 3, or 4 in the two-band Hamiltonian with crystal symmetries. However, while charge-1, charge-2, and even charge-4 Weyl points have been observed in various systems, the experimental observation of the charge-3 Weyl point (despite theoretical predictions) remains scarce. Here, we report the experimental observation of a pair of charge-3 Weyl points in a three-dimensional acoustic crystal with $C_{6z,3}$ screw symmetry, which exhibits unique hourglass-type band structures. The existence of three branches of surface arcs linked to each charge-3 Weyl point is confirmed by experimental observations, consistent with tight-binding models and numerical calculations. By projecting paired charge-3 Weyl points onto the top surface, the sixfold helical surface arcs are further observed. Our findings locate the missing experimental piece of the family of topological acoustic Weyl semimetals.

The in-plane anomalous Hall effect occurs when the magnetization lies within the same plane as the electric field and the Hall current, and requires magnetic point groups lacking rotational or mirror symmetries. While it is observed in both Weyl semimetals and elemental ferromagnets, the microscopic role of higher-order multipoles remains unclear. Here, we develop a microscopic framework that combines time-reversal-symmetric Wannier functions with a symmetry-adapted multipole basis to decompose the first-principles Wannier Hamiltonian into electric, magnetic, magnetic-toroidal, and electric-toroidal multipoles. This approach allows us to selectively analyze multipole components of the Wannier Hamiltonian and identify how symmetry-classified terms affect the angular dependence of the conductivity. Applying this framework to body-centered cubic iron, we find that high-rank magnetic and magnetic-toroidal terms produce angular variations comparable to those from magnetic-dipole terms, and that magnetic-toroidal 16-poles, in particular, give opposite-sign features. Guided by this multipole analysis, we further examine uniaxial strain along the [103] direction as an example of externally tuning the angular response. The strain substantially modifies the angular dependence, illustrating that multipole-resolved Hamiltonian analysis can provide microscopic guidance for understanding and controlling the in-plane anomalous Hall effect.

Predicting quasiparticle energies in materials requires expensive numerical evaluations of the electron self-energy. This limits calculations to ordered systems with small unit cells. Here, using symbolic regression, we show that the GW self-energy can be accurately approximated with compact analytical functions of physically motivated Kohn-Sham descriptors. These expressions can be learned from a single GW calculation in the ordered phase and remain accurate under symmetry breaking induced by quantum and thermal fluctuations, elastic deformations, and amorphous disorder. This development enables routine GW calculations of complex materials with thousands of atoms at a computational cost comparable to semilocal density functional theory. We demonstrate the accuracy of this approach for covalent semiconductors, ionic insulators, and two-dimensional materials. These results establish symbolic regression as a viable route to predictive, interpretable, and transferable many-body electronic structure models.

The photogalvanic effect (PGE), a fundamental nonlinear optical phenomenon in noncentrosymmetric materials, generates direct photocurrent under polarized light. Using quantum kinetic theory within the relaxation-time approximation, we theoretically investigate the PGE as a probe of quantum geometry in anisotropic type-I and type-II semi-Dirac (SD) systems, characterized by distinct electronic structures. We systematically analyze various microscopic contributions to the PGE conductivity, including injection, shift, resonance, higher-order pole, and anomalous terms, and emphasize their connections to different quantum geometric quantities, namely Berry curvature, quantum metric, and metric connection. By studying the frequency and chemical-potential dependence of the PGE conductivity in SD systems, we find that the optical conductivities in the type-II case are significantly enhanced relative to those in type I. For the circular PGE (CPGE), Berry-curvature-driven contributions remain qualitatively similar in both phases, whereas the linear PGE (LPGE) displays clear qualitative differences. In particular, the $xxx$ component of the shift conductivity in the type-II phase reverses sign upon tuning the perturbation parameter $\delta$, providing a direct signature of the Lifshitz transition. In contrast, other components remain sign invariant, as in type-I SD systems. These combined CPGE and LPGE signatures provide an unambiguous distinction between the two SD phases. The predicted effects, realizable in ${\mathrm{TiO}}_2/{\mathrm{VO}}_2$ heterostructures, establish PGE as a sensitive probe of quantum geometry with potential applications in polarization-selective photodetection, optical rectification, and next-generation optoelectronic devices.

Generating elliptically polarized higher-order harmonics is essential for probing a wide range of chiral-sensitive light-matter interactions in nature. We demonstrate that semi-Dirac semimetals produce efficient odd-order harmonics under circularly polarized driving fields, remarkably contrasting with known two-dimensional semimetals, where circular polarization typically suppresses high-harmonic generation. The underlying mechanism is attributed to anisotropy-induced dipole coupling, which manifests distinctly in the ellipticity dependence of the harmonic yield. Specifically, the total yield is minimal for linear polarization and rises sharply as the polarization approaches circular, exhibiting nonmonotonic, harmonic-specific behavior. We find that the polarization dependence exhibits a pronounced twofold anisotropy, with each harmonic order showing a distinct angular distribution of maximum intensity. This characteristic anisotropy arises directly from the unique band dispersion of semi-Dirac semimetals. Our results not only uncover a link between anisotropic dispersion and strong-field nonlinear optics, but also position semi-Dirac semimetals as promising platforms for symmetry-engineered and polarization-tailored ultrafast light-matter control.

Generating and controlling spin current in miniaturized magnetic quantum devices remains a central objective of spintronics, due to its potential to enable future energy-efficient information technologies. Among the existing magnetic phases, altermagnetism has recently emerged as a highly promising platform for spin current generation and control, going beyond ferromagnetism and antiferromagnetism. Here, we propose a symmetry-allowed spin photovoltaic effect in two-dimensional (2D) altermagnetic semiconductors that enables predictable control of giant spin injection currents. Distinct from parity-time $\left(\mathcal{PT}\right)$-antiferromagnets, Janus altermagnetic semiconductors generate not only shift current but also a unique injection current with spin momentum locked in a specific direction under linearly polarized light—a mechanism absent in $\mathcal{PT}$-antiferromagnets. Through symmetry analysis and first-principles calculations, we identify Janus ${\mathrm{Fe}}_2\mathrm{SSeO}$ as a promising candidate. Specifically, the monolayer ${\mathrm{Fe}}_2\mathrm{SSeO}$ exhibits a polarization-dependent injection conductivity reaching $\sim 1200\mu \mathrm{A}/{\mathrm{V}}^2\hslash /2e$, and the giant spin injection current can be effectively switched by rotating the magnetization direction and engineering strains. These findings underscore the potential of 2D altermagnets in spin photovoltaics and open avenues for innovative quantum devices.

Topological frustration arises when boundary conditions impose geometric frustration in a quantum system, creating delocalized defects in the antiferromagnetic ground states and profoundly altering the low-energy properties. While previous studies have been concerned with one-dimensional systems, showing that the ground state structure can be described in terms of quasiparticle excitations, the two-dimensional setting remains unexplored. We address this gap by studying a three-legged antiferromagnetic quantum Ising ladder on a torus using tensor network methods, where topological frustration is induced by an odd number of spins along both spatial directions. Our results reveal a surprising instance in which topological frustration shifts the position of the quantum critical point. By studying the entanglement structure, we find that the ground state can be characterized as hosting three delocalized quasiparticles. This work builds the quasiparticle picture of topological frustration towards higher dimensions and more complex systems than those considered so far.

Topological phases characterized by non-Abelian charges have garnered increasing attention recently. Although Floquet (periodic-driving) higher-order topological phases have been explored at the single-particle level, the role of couplings in non-Abelian topological insulators with multiple entangled energy gaps remains incompletely understood. In this work, we extend previous research by investigating higher-order topological phases featuring non-Abelian charges through Floquet engineering. Here we construct a model for two-dimensional non-Abelian higher-order topological phases on a square lattice subjected to two-step periodic driving. We find that the corner and edge states emerge and appear in all energy gaps despite the quaternion charge being trivial ($q=1$). Moreover, spatially exchanging the driving generates exotic interface modes—a hallmark of non-Abelian dynamics, namely, noncommutativity. Notably, although the composite Chern number is trivial due to $\mathcal{PT}$ symmetry, the Floquet system hosts nontrivial higher-order and interface topology characterized by the Stiefel Whitney invariant $w_2$ and gap-resolved Zak phase mismatches. We further reveal that the configuration of these quaternion-charge edge states is entirely determined by the quadruple degenerate phase-band singularities in the time evolution. Our work provides a platform for studying higher-order topological states and nonequilibrium quantum dynamics.

We present a first-principles study of the natural optical activity of the gyroelectric ${\mathrm{Pb}}_5{\mathrm{Ge}}_3{\mathrm{O}}_{11}$ crystal, explicitly accounting for spin-orbit coupling (SOC) effects. We derive a new analytical expression for the gyration coefficients within the recent framework of long-wavelength density-functional perturbation theory [Phys. Rev. Lett. 131, 086902 (2023)], which significantly improves computational efficiency by reducing the number of required response functions and includes spin-orbit coupling effects. We use this implementation to investigate the evolution of ${\mathrm{Pb}}_5{\mathrm{Ge}}_3{\mathrm{O}}_{11}^{\prime }\mathrm{s}$ optical rotation across the ferroelectric double-well, from the paraelectric $P\overline{6}$ phase to the ferroelectric $P3$ phase. Our results demonstrate that, in addition to the substantial renormalization of the double-well energy, spin-orbit coupling contributions play an equally crucial role in the natural optical activity, largely through purely electronic contributions, while SOC-induced structural relaxation effects are minor.

In this work we numerically study the effect of weak measurement on deconfined quantum critical point (DQCP). Particularly, we consider the ground state of a one-dimensional spin-$1/2$ system with next-nearest-neighbor exchange interactions $\left(K\right)$, which shows an analogous phase transition to DQCP in the thermodynamic limit. This system is in the ferromagnetic phase below the critical exchange interaction $K_c$ and in the valance bond solid phase above $K_c$. The weak measurement is carried out by coupling a secondary ancilla system to the critical system via unitary interactions and later measuring the ancilla spins projectively. We numerically calculate entanglement entropy, correlation length, and order parameters of leading postmeasurement states using uniform matrix product state representation of the quantum many-body state in the thermodynamic limit. We report asymmetric restructuring of entanglement of the postmeasurement states across the phase boundary under weak measurements. Specifically, the trajectory $(\downarrow \downarrow )$, describing a uniform measurement outcome given all the ancilla spins initiated in the same $(\downarrow )$ state, shows anomalous entanglement when increasing the strength of weak measurement. The bipartite entanglement entropy strongly increases when $K<K_c$, whereas it weakly decreases when $K>K_c$. We argue with numerical evidence that observed asymmetry in entanglement would lead to a weak first-order phase boundary in the thermodynamic limit. We also discuss important aspects in experimental observation of measurement-induced effects linked to the strength of weak measurement and probability of postmeasurement states.

Strong light-matter interaction in localized nanocavities is pivotal for quantum optics, yet conventional multipolar coupling is frequently obscured by parasitic background scattering. Here, we investigate the non-Hermitian strong coupling of pure multipolar resonances with two-dimensional excitons using core-shell heterostructures. Initially, by exciting an electric anapole state in a $\mathrm{Au}@\mathrm{Si}$ nanoparticle to neutralize electric dipole scattering, we isolate a nearly background-free magnetic dipole resonance to establish an electric-dipole-background-suppressed coupling platform. Advancing to higher-order modes, we employ a parity-matched excitation in an $\mathrm{Ag}@\mathrm{Ti}{\mathrm{O}}_2$ heterostructure to overcome the excitation bottleneck. This yields an ultrapure magnetic quadrupole state with a multipolar fraction exceeding 95% and massive Rabi splitting deep within the non-Hermitian strong-coupling regime. Furthermore, a quantum Heisenberg-Langevin formalism reveals the ultrafast temporal population dynamics, demonstrating a symmetric steady state and a 50-fs coherent energy exchange violently truncated by exotic non-Hermitian cooperative damping. Our work establishes multipolar radiation decoupling as a robust paradigm for high-order polaritonic devices.

We investigate the nonlinear Hall responses in tunable two-dimensional Dirac materials. In particular, we study quantum geometry-driven second and third-order nonlinear responses in a time-reversal symmetric Dirac semimetal that can host a single-node, a double-node, and a nodal-ring depending on the model parameters. We find that the second-order Hall (SOH) response, which originates from the Berry curvature dipole, is enhanced in the single-node semimetallic phase as compared with the double-node case when inversion symmetry is broken. In contrast, the SOH response vanishes in the nodal-ring semimetal because the inversion symmetry is retained. Notably, the third-order Hall response arising from Berry connection polarizability becomes much larger in the nodal-ring Dirac semimetal, especially when the Fermi energy lies near the band edge, than in the single- and double-node Dirac semimetals. The reason for this contrasting behavior is attributed to the distinct distribution of the Berry connection polarizability in the Brillouin zone.

Electrical control of antiferromagnetism is highly desirable for realizing low-cost and high-density spintronic devices, yet it remains a major challenge in conventional multiferroics. Here we propose a type-III multiferroics, where antiferromagnetism is driven by ferroelectric polarization, providing a potential route for controlling antiferromagnetism via electric fields. We reveal that the emergence of electric polarization could greatly change the crystal field splitting, which alters spin occupation states and, thus, induces antiparallel aligned atomic magnetic moments. Using first-principles calculations, we predict ferroelectricity-driven antiferromagnetism in a ${\mathrm{NbS}}_2$ bilayer intercalated by Ti atoms [denoted as $\mathrm{Ti}{\left({\mathrm{NbS}}_2\right)}_2]$. In the nonpolar AA stacking configuration, the two spins of $\mathrm{T}{\mathrm{i}}^{2+}$ ions are paired in the lowest singlet $d_{z2}$ orbital owing to the trigonal prismatic crystal field, leading to zero magnetic moment. While in the AB configuration with an out-of-plane polarization of 1.34 $\mu \mathrm{C}/\mathrm{c}{\mathrm{m}}^2$, the two spins are parallel in the triplet ${\mathrm{t}}_{2g}$ levels generated by the octahedral crystal field, giving rise to an atomic magnetic moment of 2 μ${}_B$ per Ti and a stripy-antiferromagnetic ground state. The discovery of antiferromagnetic type-III multiferroics would open an innovative pathway for realizing next-generation spintronic devices.

Exact results using dual unitarity largely rely on nearest-neighbor structures, while finite-range interactions typically lead to complications. Going beyond the usual nearest-neighbor setting, we introduce an analytically tractable family of finite-range kicked Ising models that admit exact closed-form entanglement dynamics. The construction is based on a staggered structure in which dual unitarity is present on sublattices that are then coupled to each other. The central observation is that these intersublattice couplings do not obstruct the dual unitarity of the resulting model. For the minimal interaction range of $r=2$, we derive exact expressions for all the $n$-Rényi entanglement entropies at all times and show that the result is the sum of the two coupled sublattice contributions. Our framework extends naturally to larger finite interaction ranges and to systems with heterogeneous local Hilbert spaces, without additional assumptions. It thus provides a controlled setting for studying exact entanglement growth beyond strictly nearest-neighbor dual-unitary models.