We develop a nonequilibrium multiorbital extension of the two-particle self-consistent theory and apply it to the bilayer Hubbard model as a minimal platform to investigate correlation effects in the presence of interlayer interactions and tunneling. The method determines vertex corrections in the spin and charge channels self-consistently at the two-particle level, thereby avoiding the spurious finite-temperature phase transitions that limit dynamical mean-field theory in two dimensions. We derive the spectral self-energy and implement the framework directly on the real-frequency axis within the Keldysh nonequilibrium Green's function formalism, enabling the treatment of both equilibrium and nonequilibrium steady states without relying on numerical analytic continuation. As an application, we demonstrate that a pseudogap can emerge in the bilayer Hubbard model when spin, charge, or excitonic fluctuations become sufficiently strong. Instabilities in different channels are also evaluated in an unbiased manner across the parameter space. Remarkably, we find that the excitonic susceptibility grows with increasing interlayer bias, before it gets suppressed at large biases by the charge imbalance between the layers. This work establishes a versatile and computationally efficient framework for investigating correlated multiorbital systems under nonequilibrium conditions.

We analyze a plasmonic model on a honeycomb lattice of metallic nanodisks that hosts nodal lines enclosing the K points. An effective second-neighbor hopping between opposite synthetic spin states shifts the Dirac cones, leaving behind a nodal line at zero energy. Using both continuum and tight-binding models, we show that there is an ideal limit of the plasmonic crystal in which symmetries enforce the existence of nodal lines enclosing the K points. These nodal lines are not directly gapped even when these symmetries are weakly broken. The existence of the nodal lines in the weakly symmetry-broken case is verified using full-wave electromagnetic simulations. We also show that the nodal line degeneracies can be relieved by introducing a Kekulé distortion that acts to mix the nodal lines enclosing the K and ${\mathrm{K}}^{\prime }$ points. Our findings open pathways for designing unique plasmonic and photonic devices without reliance on complex symmetry engineering, presenting a convenient platform for studying nodal structures in two-dimensional systems.

We investigate the electronic structure of americium (Am) across its four experimentally confirmed high-pressure phases, Am-I ($P{6}_3/mmc$), Am-II ($Fm\overline{3}m$), Am-III ($Fddd$), and Am-IV ($Pnma$), up to 100 GPa, using density functional theory combined with an embedded dynamical mean-field approach. Our calculated density of states reproduces the key spectral features observed in ultraviolet photoemission spectroscopy for the Am-I phase. The results reveal a progressive pressure-driven evolution from purely localized $5f$ states of Am-I and Am-II toward the onset of delocalization. This trend is evidenced by a systematic spectral weight transfer toward the Fermi level, enhanced $f\text{−}c$ hybridization, and increasingly pronounced valence state fluctuations characterized by the mixing of $5f^5, 5f^6$, and $5f^7$ electronic configurations. Crucially, despite these delocalization trends, the $5f$ partial density of states remains strictly depleted at the Fermi level in all phases. In our calculations Am-IV represents a distinct “localized but hybridized” state, in which the $5f$ electrons retain their localized character while beginning to participate in bonding. This interpretation reconciles conflicting experimental reports and establishes Am as a quintessential platform for understanding the localized to itinerant transition in actinides. This unified picture not only resolves long-standing controversies surrounding the nature of Am's high-pressure phases but also provides a robust microscopic framework for predicting the behavior of neighboring transuranium elements under extreme conditions.

The anomalous Nernst and anomalous thermal Hall effects are prominent manifestations of Berry curvature in topological magnets. However, their electrical and thermal responses are governed by different moments of the Berry curvature spectrum, making their simultaneous enhancement in a single material a significant challenge. Here, we propose a universal strategy to overcome this fundamental trade-off by exploiting the unique properties of flat bands. We demonstrate that in magnetic Weyl semimetals, suppressing band dispersion to approach a flat band concentrates the Berry curvature, leading to a synergistic enhancement of both the anomalous Nernst and thermal Hall conductivities. This mechanism is systematically validated, first through a minimal Weyl model and then in a realistic pyrochlore lattice tight-binding model. To bridge theory with experiment, we employ first-principles calculations to identify candidate materials such as ${\mathrm{ZnV}}_2{\mathrm{O}}_4$ and ${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$, demonstrating that their native flat bands provide a platform for strain engineering to directly control the transverse thermoelectric and thermal responses. Our work establishes flat bands as a powerful design principle for developing high-performance energy conversion and topological quantum devices.

We study a class of quantum phase transitions between featureless bosonic atomic insulators in $(2+1)$ dimensions, where each phase exhibits neither topological order nor protected edge modes. Despite their lack of topology, these insulators may be obstructed in the sense that their Wannier centers are not pinned to the physical atomic sites. These insulators represent distinct phases, as no symmetry-preserving adiabatic path connects them. Surprisingly, we find that for certain lattices, the critical point between these insulators can host a conformally invariant state described by quantum electrodynamics in $(2+1)$ dimensions (${\mathrm{QED}}_3$). The emergent electrodynamics at the critical point can be stabilized if embedding the microscopic lattice symmetries suppresses the proliferation of monopoles, suggesting that even transitions between trivial phases can harbor rich and unexpected physics. We analyze the mechanism behind this phenomenon, discuss its stability against perturbations, and explore the embedding of lattice symmetries into the continuum through anomaly matching. In all the models we analyze, we confirm that the ${\mathrm{QED}}_3$ is indeed emergeable, in the sense that it is realizable from a local lattice Hamiltonian.

We develop an energy-space density matrix framework to investigate the interaction of extremely short optical pulses (ESPs) with transparent conducting oxides (TCOs). This approach captures not only electron populations, material polarization, and the permittivity, but also the quantum coherences between states. Compared to traditional momentum-space models, the energy-space formulation offers substantial computational simplification while retaining accuracy. Building on but going beyond the scope of Ref. [Un et al. (unpublished)], we focus on dynamical features previously unexplored. Our formulation reveals clear signatures of quantum coherence in the net absorption dynamics and highlights the emergence of strong excited-state absorption under intense excitation. Furthermore, we investigate the influence of pump pulse intensity on the local field's duration, spectral broadening, and shift, and phase induced by carrier dynamics, highlighting the absorptive nature of the nonlinear response. Our results provide a unified framework for understanding nonlinear light-matter interaction in dispersive, low-density electron systems driven far from equilibrium by intense broadband excitation.

We study ballistic electron transport through electrostatic barriers in AB-stacked bilayer graphene within a full four-band framework. A mode-resolved analysis reveals how propagating and evanescent channels couple across electrostatic interfaces and how channel selectivity governs transport at normal incidence. We show that perfect transmission can occur at discrete energies due to phase matching of a single internal mode within an individual barrier, without activating the decoupled channels. This effect is interpreted as a phase-matching cavity, namely, an effective cavity formed by internal phase coherence inside the barrier, which yields perfect transmission at discrete energies without true bound states and without opening additional transport channels. For single- and double-barrier geometries, we derive compact analytical expressions for the transmission and identify the corresponding resonance conditions. Extending the analysis to multibarrier structures using a transfer-matrix approach, we demonstrate how perfect resonances driven by internal phase matching coexist with Fabry-Pérot–type resonances arising from interbarrier interference. Our results provide a unified, channel-resolved description of tunneling suppression and resonance-assisted transport in bilayer graphene barrier systems.

We demonstrate the existence of an unconventional pairing state in photodoped Mott insulators on ladder and quasi-two-dimensional geometries, characterized by quasi-long-range doublon-holon correlations that signal Mott exciton condensation. The doublon-holon pairing exhibits correlations of $d$-wave-like symmetry, reminiscent of superconducting pairing in chemically doped Mott insulators. By constructing the phase diagram, using density matrix renormalization group, we reveal that the doublon-holon pairing state in the photodoped ladder emerges between the spin-singlet, charge-density-wave, and $\eta$-pairing phases. Our study suggests that the interplay of charge, spin, and $\eta$-spin degrees of freedom can give rise to exotic quantum many-body states in photodoped Mott insulators.

Large-angle twisted bilayer graphene (TBLG) realizes a multicomponent quantum Hall (QH) platform of spin, valley, and layer pseudospins with strong Coulomb interaction-driven symmetry broken phases. Here, we investigate the low energy Landau-level spectrum of layer-decoupled TBLG and identify skyrmion-textured charged excitations and a field-induced insulating transition to an intervalley coherent state at zero-filling factor. Symmetric potential difference perpendicular to TBLG demonstrated layer coherent population of ground states with uniform energy barriers, while the charge imbalance in the layers at finite displacement field led to multidomain nucleation and a pronounced hysteresis in the exchange-dominated transport regime suggesting first order phase transitions between different QH ferromagnetic ground states.

We demonstrate photonic control of radiative heat transport in nanoscale networks through phase-controlled interference between elastic and inelastic Floquet scattering channels induced by temporal permittivity modulation. Relative modulation phases select constructive or destructive interference, enabling directional thermal-photon currents and heat splitting even at thermal equilibrium. Modulation amplitude and frequency further tune the enhancement, suppression, and redistribution of energy flow. This interference-based mechanism enables thermal routing and logic operations and provides a general platform for reconfigurable photonic heat management at the nanoscale.

Topological phase transitions can be remarkably induced purely by manipulating gain and loss mechanisms, offering a novel approach to engineering topological properties. Recent theoretical studies have revealed gain-loss-induced topological disclination states, along with the associated fractional charge trapped at the disclination sites. Here, we present the experimental demonstration of topological disclination states in a purely lossy electric circuit. By designing alternating lossy electric circuit networks that correspond to the disclination lattice, we observe a voltage response localized at the disclination sites and demonstrate the robustness of these states against disorder. Furthermore, we measure the charge distribution, confirming the presence of fractional charge at the disclination sites, which gives rise to the topological disclination states. Our experiment provides direct evidence of gain-loss-induced topological disclination states in electric circuits, opening new possibilities for applications in classical systems.

We examine the relation between the quantum Landau-Lifshitz equation ($q$-LL) [Wieser, Phys. Rev. Lett. 110, 147201 (2013)] and quantum Landau-Lifshitz-Gilbert equation ($q$-LLG) [Liu et al., Phys. Rev. Lett. 133, 266704 (2024)], two nonlinear purity preserving master equations that extend classical atomistic spin dynamics into the quantum regime. While the classical LL and LLG counterparts for any number of spins are known to be equivalent, i.e., give identical spin trajectories up to a rescaling of the time parameter, the quantum formulations are equivalent only in certain cases, such as for pure states or for arbitrary single spin-$\frac{1}{2}$ states. Here, we demonstrate that this equivalence breaks down even at the level of a single spin, provided $s\ge 1$. Focusing on a spin-1 particle in an anisotropic crystal field, we show that the $q$-LL and $q$-LLG equations generate inequivalent time evolution. We introduce temporal rescaling misfits that quantify the inequivalence of the two types of dynamics. Although our results highlight fundamental differences in dissipation mechanisms encoded in these equations, the resulting trajectories remain qualitatively similar for this system.

Magnetic frustration in kagomé lattice materials has attracted considerable attention as a source of novel magnetic properties and magnetotransport phenomena. Here we report experimental evidence for collinear ferrimagnetic ordering and multiple field-induced magnetic transitions in $\mathrm{T}{\mathrm{b}}_3\mathrm{R}{\mathrm{u}}_4\mathrm{A}{\mathrm{l}}_{12}$ with a breathing kagomé lattice, revealed by field-dependent resonant x-ray scattering measurements performed at 8 K. The Hall response shows significant deviation from the conventional behavior above the ordering temperature, which can be plausibly interpreted in terms of thermally induced scalar spin chirality. Theoretical calculations reveal the emergence of net scalar spin chirality, whose magnitude depends on Ising-type magnetic anisotropy, in good agreement with experimental results on breathing kagomé magnets with different magnitude of the easy-axis anisotropy. This study highlights that nontrivial magnetotransport phenomena in breathing kagomé magnets may arise from thermally fluctuating spin moments with finite scalar spin chirality, even when the ground state is a collinear ferrimagnet.

We predict the realization of ultrastrong coupling between magnons of antiferromagnets and photons in superconductor/antiferromagnet/superconductor heterostructures at terahertz frequencies, from both quantum and classical perspectives. The hybridization of the two magnon modes with photons strongly depends on the applied magnetic field: at zero magnetic field, only a single antiferromagnetic mode with a lower frequency couples to the photon, forming a magnon-polariton, while using a magnetic field activates coupling for both antiferromagnetic modes. The coupling between magnon and photon is ultrastrong with the coupling constant $\sim 100$ GHz exceeding 10% of the antiferromagnetic resonant frequency. The superconductor modulates the spin of the resulting magnon-polaritons and the group velocity, achieving values amounting to several tenths of the speed of light, which promises strong tunability of magnon transport in antiferromagnets by superconductors.

We present a generalized mean-field description of spinor polariton fluids and introduce a model that incorporates pure energy relaxation, while conserving particle number. This model constitutes the spinor extension of our quantum-hydrodynamic theory, enabling a consistent treatment of two-component condensates with polarization (pseudospin) degrees of freedom. Starting from a two-component hydrodynamic formulation, we derive a closed set of equations in which pure energy relaxation acts through both the usual density/phase and spin (polarization) channels. We show how these relaxation pathways govern polarization dynamics, determine the stability of stationary polarized states, and modify the spectrum of elementary excitations, with particular emphasis on a condensate in an external magnetic field. Although we focus on exciton-polaritons in semiconductor microcavities, our approach can be applied to other spinor bosonic condensates where spin relaxation plays a significant role.

We investigate the interplay between spin currents and spin waves in nanofabricated Permalloy waveguides with geometrical constrictions. Using propagating spin-wave spectroscopy, micromagnetic simulations, and analytical modeling, we provide experimental evidence that spin-wave phase can be modulated by inhomogeneous spin-transfer torques generated by current-density gradients shaped by the constriction geometry. Narrower constrictions enhance these gradients and modify the internal field for Damon–Eshbach spin waves, resulting in pronounced changes in spin-wave group velocity and phase. We show a quantitative experimental demonstration of deterministic spin-wave phase modulation enabled by geometry-engineered nonuniform spin-transfer torques. Beyond enabling a scalable route to magnonic interferometry—a building block for spin-wave-based computing—our findings establish a platform to control spin-wave dynamics in spatially varying current landscapes, relevant for analog-gravity experiments in condensed matter systems.

Efficient spin-to-charge is crucial for developing high-performance spintronic devices, such as terahertz (THz) emitters and spin batteries. Here, we demonstrate that precise engineering of the Pt layer in $\mathrm{FeNi}/\mathrm{Pt}/\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$, using scalable magnetron sputtering, significantly enhances conversion efficiency over a broad frequency range (from GHz to THz). Terahertz emission spectroscopy and ferromagnetic resonance measurements identify an optimal Pt thickness of $\approx 2\mathrm{nm}$, where the THz emission intensity increases by a factor of $\approx 8$ compared with a sample without the Pt layer. In the 2 nm Pt samples, both the THz emission amplitude and effective spin Hall angle exhibit a monotonic increase with temperature. First-principles calculations indicate that this enhancement arises mainly from Rashba-split surface states at the Pt/$\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$ interface, rather than from preserved topological surface states. These findings highlight the crucial role of Pt interface engineering in boosting spin-to-charge conversion in topological insulators, with promising implications for broadband communication and information processing.

Topological aspects in altermagnets have come into focus recently, and tuning the antiferromagnetic state into an altermagnetic phase remains an active frontier. We realize both within a rutile superlattice here in this paper. With first-principles calculation, we show that a uniaxial strain of only $0.5\%$ along the $c$ axis converts the ${\left({\mathrm{CrO}}_2\right)}_1/{\left({\mathrm{TaO}}_2\right)}_2$ rutile superlattice from a trivial antiferromagnet into an altermagnet with topology accompanied by a weak spin-orbit coupling (SOC). The strain opens a spin-dependent band splitting of $\sim 1.1\text{eV}$ and, despite the weak SOC together with in-plane magnetic moment orientation, generates an intrinsic anomalous Hall conductivity of order ${10}^3\text{S/cm}$, a comparable magnitude to that in ferromagnetic Weyl semimetals. Here, the Tiny SOC with an in-plane Néel orientation gaps out the Weyl nodal rings, giving rise to 16 Weyl points in the superlattice. Thus, we point out a simple route toward strain- and field-tunable, low-dissipation altermagnetic electronics.

The properties of spin fluctuations in antiferromagnets are largely unexplored, in particular at ultrafast timescales. Here, we employ femtosecond noise correlation spectroscopy to experimentally study magnetization fluctuations in the canted antiferromagnet $\mathrm{S}{\mathrm{m}}_{0.7}\mathrm{E}{\mathrm{r}}_{0.3}\mathrm{Fe}{\mathrm{O}}_3$ across its spin-reorientation transition and under external magnetic fields. By comparing our measurements to atomistic spin noise and Monte Carlo simulations, we find that the amplitude of the spin noise is governed by the free energy, with stronger fluctuations in regions where the potential landscape softens. We furthermore demonstrate that external magnetic fields suppress spin fluctuations and enhance the quasiferromagnetic magnon frequency by effectively stiffening the potential. These results highlight an effective route for tuning ultrafast magnetization fluctuations via external parameters.

We investigate the effects of Cr off-stoichiometry on the structural, magnetic, thermodynamic, and electrical transport properties of the antiferromagnetic compound CrSb. Single-phase hexagonal NiAs-type structure is stabilized only in the Cr-rich regime, where excess Cr atoms preferentially occupy the interstitial trigonal bipyramidal $2d$ sites, as confirmed from the x-ray diffraction study. Synchrotron-based x-ray absorption fine-structure measurements reveal a progressive increase in local structural disorder with increasing Cr concentration, particularly within the Cr sublattice. Magnetization measurements show a pronounced low-temperature upturn in susceptibility and nonlinear field-dependent behavior, which can be consistently described by the formation of short-range magnetic clusters associated with interstitial Cr moments embedded in the antiferromagnetic CrSb matrix. Specific-heat measurements indicate a finite electronic density of states at the Fermi level with a nonmonotonic evolution of the Sommerfeld coefficient with Cr content, reflecting the interplay between electronic delocalization and disorder-induced localization. Electrical transport measurements confirm metallic conduction across all compositions and reveal the emergence of an antiferromagnetic gap at low temperatures with increasing Cr concentration. These results demonstrate a strong coupling between off-stoichiometry, local structural disorder, magnetic correlations, and charge transport in ${\mathrm{Cr}}_{1+x}\mathrm{Sb}$ and establish controlled Cr occupancy as an effective route for tuning magnetic interactions and electronic responses relevant to altermagnetic systems.