Floquet engineering via external periodic fields has emerged as a powerful dynamic regulation strategy for topological semimetals, yet most existing studies rely on high-frequency approximations with limited applicability across the full frequency domain. In this paper, we investigate the modulation of a Dirac semimetal system driven by an optical comb and, more importantly, derive an exact analytical solution to the corresponding Floquet Hamiltonian, which enables unapproximated exploration of the system across the entire frequency domain. We show that the exact solution captures characteristic features beyond the low-order approximation in the high-frequency regime. With decreasing driving frequency, the system exhibits distinct higher-order hinge states. In the low-frequency regime, nodal lines emerge as a result of the periodic field. Our findings demonstrate that the proposed periodic electric pulses, together with the exact analytical method, provide a rigorous theoretical framework for full-frequency Floquet engineering of topological semimetal systems.

We extend a recently defined measure of symmetry breaking, the entanglement asymmetry, to higher-form symmetries. In particular, we focus on Abelian topological order in two dimensions, which spontaneously breaks a 1-form symmetry. Using the toric code as a primary example, we compute the entanglement asymmetry and compare it to the topological entanglement entropy. We find that while the two quantities are not strictly equivalent, both are subleading corrections to the area law and can serve as order parameters for the topological phase. We generalize our results to Abelian topological order and express the maximal entanglement asymmetry in terms of the number of anyon species. Finally, we discuss how the scaling of entanglement asymmetry correctly detects topological order in the deformed toric code, where 1-form symmetry breaking persists even in a nontopological phase.

Nonlinear four-wave mixing processes are a powerful technique to unravel ultrafast dynamics in solid-state systems. Here, we employ attosecond four-wave mixing spectroscopy with one extreme ultraviolet (XUV) pump and two independently delayed, noncollinear near-infrared (NIR) probes to resolve the ultrafast decoherence of both dipole-allowed and dipole-forbidden core excitons at the ${\mathrm{Na}}^{+}{\mathrm{L}}_{2,3}$ edge in sodium fluoride (NaF). The decoherence times of the core excitons are observed to be much faster than the 8 fs limit of the instrument response time, which is attributed to strong exciton–phonon coupling. Furthermore, polarization control of the NIR probes (perpendicular and parallel polarizations) reveals that the bright core excitons exhibit $s$-like orbital angular momentum, while dark core excitons, reached by two-photon excitation, exhibit $p$-like orbital angular momentum.

The interplay of multiorbital physics and nonlocal self-energy effects is studied within an effective three-orbital model for the high-pressure normal state of superconducting bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. The model is solved within an advanced many-body framework capturing $k$-dependent correlations beyond dynamical mean-field theory. Different low-energy scenarios subtly depend on the strength of the interorbital interaction, either placing the notorious flat $\gamma$ quasiparticle band in the occupied part of the spectrum, or letting it cross the Fermi level. In the latter case, intriguing spin-polaron formation due to the scattering of electrons with paramagnon excitations takes place. This leads to bound states appearing as a shadow band with incoherent low-energy spectral weight below the Fermi level. Our results uncover additional competing states that exist in bilayer nickelates and could explain the controversy of recent angle-resolved photoemission experiments.

We study a dissipative version of the Anderson Impurity model, where an interacting impurity is coupled to a fermionic reservoir and exposed to Markovian dissipation in the form of two-body losses. Using a self-consistent hybridization expansion based on the noncrossing approximation (NCA), we compute the dynamics of the impurity, its steady state, and a spectral function. We show that the interplay between strong Coulomb repulsion and correlated dissipation gives rise to robust signatures of Kondo physics both at weak and strong losses. These include a strongly suppressed spin relaxation rate, displaying a characteristic Kondo-Zeno crossover, and a spectral function where the doublon band is quickly destroyed by dissipation while the coherent Kondo peak remains visible for weak losses, then disappears at intermediate values and finally re-emerges as the system enters the Kondo-Zeno regime. As compared to the case of single-particle losses, we show that two-body dissipation protects Kondo physics. The picture obtained with NCA is confirmed by numerical simulations of exact dynamics on finite-size chains. We interpret these results using a dissipative Schrieffer-Wolff transformation, which leads to an effective Kondo model with residual impurity-bath losses, which are suppressed by strong correlations or strong losses.

${\mathrm{YbZn}}_2{\mathrm{GaO}}_5$ has recently emerged as a structurally ideal triangular-lattice antiferromagnet and a promising candidate for hosting a U(1) Dirac quantum spin-liquid (QSL) ground state. However, signatures of broadened crystal electric field (CEF) excitations have raised questions about potential site disorder and its impact on the intrinsic spin dynamics. In this study, we employ ${}^{71}\mathrm{Ga}$ nuclear magnetic resonance (NMR) and muon spin relaxation ($\mu \mathrm{SR}$) to microscopically probe both the structural and magnetic properties of ${\mathrm{YbZn}}_2{\mathrm{GaO}}_5$. NMR spectra reveal two inequivalent ${}^{71}\mathrm{Ga}$ sites and a broad distribution of quadrupolar frequencies, providing clear evidence of ${\mathrm{Ga}}^{3+}/{\mathrm{Zn}}^{2+}$ site mixing and local CEF randomness. The NMR spin-lattice relaxation rate exhibits, down to 1.3 K, a power-law temperature dependence, consistent with persisting spin dynamics below the exchange energy scale in a frustrated magnet. Complementary $\mu \mathrm{SR}$ measurements further show that the spin dynamics persist down to 30 mK, with no signs of spin freezing. Together, these results establish that ${\mathrm{YbZn}}_2{\mathrm{GaO}}_5$ presents substantial structural disorder, while the persistence of dynamic spin fluctuations down to the lowest temperatures may indicate the survival of QSL-like excitations despite such disorder.

This paper presents a detailed theoretical investigation of the energy spectrum, band gaps, topological and collective properties, and linear response in $d$-wave altermagnets in the presence of an off-resonance optical dressing field. We consider the altermagnets with both $d_{x^2-y^2}$ and $d_{xy}$ symmetries and focus on anisotropic optical driving fields applied to the initially anisotropic and nonlinear electron Hamiltonian. We have uncovered several crucial properties of the resulting electron-dressed states; specifically, we found that a finite band gap is opened by linearly polarized irradiation, a phenomenon not observed in Dirac materials. Some of the crucial properties of the electron-dressed states in the presence of linearly polarized light can be uncovered only in the second-order perturbation expansion, which is often omitted. We found that introducing an anisotropic driving field leads to several subtle yet important changes in the Edelstein susceptibilities of altermagnets, enabling the fine-tuning of their spin polarizations. We calculate the Berry curvature and Chern numbers for various types of altermagnets and obtain closed-form analytical expressions for circularly polarized irradiation. We demonstrate that the optical driving field can generate finite Berry curvature and Chern numbers in the absence of altermagnetic order. All these results are expected to make a crucial contribution to the rapidly developing fields of spintronics and device physics.

Motivated by recent experiments, here we identify the valley-coherent charge density wave (VC-CDW) in the nondegenerate quarter metal for the entire family of chirally stacked $n$ layer graphene, encompassing rhombohedral multilayer, Bernal bilayer, and monolayer cousins. Besides the hallmark broken translational symmetry, yielding a modulated charge density over an enlarged unit cell with a characteristic $2\mathbf{K}$ periodicity, where $\pm \mathbf{K}$ are the valley momenta, this phase lacks the threefold ($C_3$) rotational symmetry but only for $n=1$ and even integer $n$. The VC-CDW then represents a stripe order, as observed in hexalayer graphene [arXiv:2504.05129], but preserves the $C_3$ symmetry for other odd integer $n$ as observed in trilayer graphene [Nat. Phys. 20, 1413 (2024); arXiv:2411.11163]. From a universal Clifford algebraic argument, we show that the VC-CDW and an anomalous Hall order can lift the residual valley degeneracy of an antiferromagnetically ordered spin-polarized half metal, when these systems are subject to perpendicular displacement fields. Only the anomalous Hall order displays a hysteresis in off-diagonal resistivity, as observed in all the systems with $2\le n\le 6$. We showcase a confluence of VC-CDW and anomalous Hall orders within the quarter metal, generically displaying a regime of coexistence, otherwise separating the pure phases.

The time-evolving matrix product operator (TEMPO) method has proven to be a powerful method to study the long-time dynamics of bosonic impurity problems where a small system is linearly coupled to a noninteracting bosonic bath. However, current developments of TEMPO have mostly focused on the case of diagonal system-bath coupling, i.e., ${\sum }_k\widehat{A}(V_k{\widehat{b}}_k^{†}+\mathrm{H}.\mathrm{c}.)$, with $\widehat{A}$ a Hermitian operator of the system. Based on the process tensor framework, we extend TEMPO to the more general case of off-diagonal system-bath coupling in the form ${\sum }_k(V_k\widehat{A}{\widehat{b}}_k^{†}+\mathrm{H}.\mathrm{c}.)$, where $\widehat{A}$ could be non-Hermitian. As applications, we study the real-time dynamics of a spin that is coupled to a sub-Ohmic bath via the Jaynes-Cummings-type system-bath coupling and compare it against the standard spin-boson model, where we show that the commonly used rotating-wave approximation could be very poor for this bath. We also study the imaginary-time evolution of a bosonic impurity with nonzero on-site interaction that is coupled to a sub-Ohmic bath, to illustrate the flexibility of our method. Our method provides a unified framework to understand different variants of TEMPO and is a promising building block for an impurity solver in the bosonic dynamical mean-field theory for the normal phase with a scalar hybridization function.

Controlling magnetic coupling at superconductor-magnet interfaces is a fundamental challenge. Using numerical renormalization group calculations on a strongly correlated molecular dimer coupled to two superconducting electrodes, we report a two-stage quantum phase transition driven solely by the superconducting gap $\mathrm{\Delta }$. As $\mathrm{\Delta }$ increases, the system first transits at ${\mathrm{\Delta }}_{c1}$ from an underscreened Kondo-dominant state to a superconducting-dominant one. Simultaneously, the interorbital exchange mediator shifts from metallic itinerant electrons to virtual single-particle excitations within the gap-a renormalized Ruderman-Kittel-Kasuya-Yosida interaction that sustains ferromagnetic order. Remarkably, at a second critical point ${\mathrm{\Delta }}_{c2}$, the mediator then undergoes a fundamental switch to virtual Cooper pairs from the condensate, triggering an abrupt reversal of the spin correlation from ferromagnetic to antiferromagnetic. This sequential exchange mediator switching, distinct from the conventional picture of a smoothly enhanced Yu-Shiba-Rusinov exchange, establishes a paradigm for actively tuning quantum magnetic states in superconducting heterostructures.

Monitored quantum circuits in which entangling unitary dynamics compete with projective local measurements can host measurement-induced phase transitions witnessed by entanglement measures at late times. Adding feedback conditioned on the measurement outcomes gives rise to another type of phase transition witnessed by local order parameters and correlation functions. These transitions, known as control or absorbing-state transitions, generically occur within the area-law entanglement phase and are thought to be governed by classical physics in that their critical exponents match those of the classical limit of the model. In this work, we examine quantum features of these transitions, focusing on a Bernoulli circuit model with a well-defined classical limit, in the presence of unitary dynamics, measurements, and feedback. First, we demonstrate that, in the local basis defined by the absorbing state, the steady-state quantum coherence undergoes a phase transition at the control transition, where its logarithm changes discontinuously from volume- to area-law scaling. Second, we analyze the control transition from the perspective of fluctuations in observables, which carry two contributions: classical fluctuations over circuit realizations (present in the classical limit), and quantum fluctuations over trajectories and states (both absent in the classical limit). Both contributions can be estimated in experiments without postselection. The circuit-to-circuit fluctuations, the dominant contribution, carry the critical behavior of the classical limit. However, the subleading quantum fluctuations that represent fluctuations between different quantum “worlds” also go critical at the control transition. These critical quantum fluctuations at the control transition also occur in other models, and we discuss how they can be measured experimentally without postselection.

Motivated by the orientation-dependent spin splitting and vanishing net magnetization of altermagnets, we study $d$-wave altermagnetic Josephson junctions (JJs) with a focus on the emergence and controllability of non-Hermitian degeneracies [or exceptional points (EPs)] where both eigenvalues and eigenvectors coalesce. Unlike conventional JJs, the altermagnetic order induces spin- and orientation-dependent Andreev bound states, offering additional control of the Josephson effect. We show that the position of EPs as a function of the superconducting phase difference $\varphi$ can be tuned by the crystal orientation, strength of the altermagnetic order, Rashba spin-orbit coupling, and the degree of non-Hermiticity. Furthermore, the number of EPs is found to be directly tunable by altermagnetic properties. The total supercurrent associated with different transverse momentum $k_y$ shows a smooth behavior but sensitive to the crystal orientation and other properties of the altermagnetic JJ. These findings demonstrate a pathway to realizing distinctive non-Hermitian phenomena arising from the interplay among non-Hermiticity, Rashba interaction, superconductivity, and altermagnetism.

In this manuscript we consider a superconducting film in the vicinity of the critical temperature and presence of the proximity effect. We analytically solve the corresponding linearized Usadel equation and the self-consistency equation, defining the critical temperature. This is a system of coupled differential and integral equations for the anomalous Green's function and the order parameter of the superconductor. The proximity effect defines the boundary conditions. The formal solution of the system is found for the general case of the linearized boundary conditions defined by the proximity effect, reducing the set of equations to an eigenvalue problem. The latter defines the critical temperature of the superconducting phase transition and the spatial distributions of the anomalous Green's function and the superconducting order parameter.

Thermal switching is an advanced smart thermal control technology in thermal management systems, such as refrigeration, thermal resistors, and space technology. Controlling lattice thermal conductivity (${\kappa }_{\mathrm{l}}$) through structural phase transitions provides an effective strategy for thermal switching applications. Here, we investigate the dual-channel thermal transport in polar and antipolar phases of NaZnSb using first-principles calculations. Compared with the polar phase, the antipolar phase exhibits a markedly lower ${\kappa }_{\mathrm{l}}$, leading to thermal switching ratios of 2.51, 2.06, and 1.75 at 300, 500, and 700 K, respectively. Such large ratio is mainly induced by the particlelike thermal conductivity (${\kappa }_{\mathrm{p}}$). Spectral and cumulative ${\kappa }_{\mathrm{p}}$ analyses reveal that heat transport in both phases is dominated by acoustic and low-frequency optical phonons with mean free paths of 2–20 nm. The reduced ${\kappa }_{\mathrm{p}}$ in the antipolar phase originates from stronger LA-optical phonon mixing, lower phonon group velocities, higher scattering rates, larger phase space, and enhanced anharmonicity. The projected crystal orbital Hamilton population analyses further show stronger Zn-Sb and Sb-Sb antibonding interactions in the antipolar phase, which weaken bonding, enhance atomic vibrations, and suppress sound velocity. This work elucidates the microscopic origins of reduced thermal conductivity across the polar to antipolar transition, providing valuable guidance for designing ferroelectric/antiferroelectric thermal switching materials.

We investigate a many-body extended Aubry-André-Harper model and find that the many-body critical phase becomes ergodic when the boundary condition is changed from open to periodic in finite systems. The resulting ergodic phase satisfies the eigenstate thermalization hypothesis and loses memory of initial states after long-time evolution. By independently tuning boundary hoppings and interactions, we identify the hopping suppression as the key microscopic mechanism underlying this behavior. More importantly, we find that when multiple zero-amplitude hoppings remain effectively operative, the many-body critical phase persists even as the interaction strength increases. In contrast, disrupting these zero-amplitude hoppings strongly destabilizes criticality and promotes thermalization. These results establish zero-amplitude hoppings as an important microscopic ingredient governing the stability of many-body criticality.

Controlling magnetic interactions at the nanoscale is crucial for the development of next-generation spintronic devices and functional magnetic materials. In this work, we investigate theoretically, by means of many-body perturbation theory, how interlayer twisting modulates magnetic interactions in bilayer van der Waals systems composed of two ferromagnetic layers. We demonstrate that the relative strengths of the interlayer Heisenberg exchange interaction, the Dzyaloshinskii–Moriya interaction, and the anisotropic exchange interaction can be significantly altered by varying the twist angle between the layers, thus leading to tunable magnetic textures. We further show that these interactions are strongly dependent on the chemical potential, enabling additional control via electrostatic gating or doping. Importantly, our approach is applicable to arbitrary twist angles and does not rely on the construction of a Moiré supercell, making it particularly efficient even at small twist angles.

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.