While cavity-magnon hybridization has revealed rich physical phenomena, its practical applications are limited by intrinsic damping in both cavity and magnon modes, a fundamental limitation that leads to short coherence times. Recently, the development of tunable macroscopic gain has shifted the focus of research from purely dissipative systems to gain-loss-balanced non-Hermitian architectures. Here, we present a pseudo-Hermitian model consisting of two magnon modes and two cavity modes arranged in a closed-loop coupling configuration that generates a gauge-invariant coupling phase distinct from conventional phase factors. We establish a direct link between the energy spectra and phase transitions, and observe exceptional points that mark the onset of pseudo-Hermitian symmetry breaking. We further demonstrate both level attraction and level repulsion: the former is associated with four phase transitions and manifests as a double-Z-shaped energy spectrum, while the latter corresponds to two phase transitions characterized by a phase-tunable repulsive gap. In the phase diagram spanned by the non-Hermiticity parameter and the gauge-invariant coupling phase, we uncover a unique correspondence: pseudo-Hermitian symmetry breaking is intrinsically linked to transitions between coherent and dissipative coupling modes, providing new strategies for controlling hybrid magnon-photon quantum states in spintronic systems.

We investigate the influence of magnetic order on the proximity-induced superconducting state in the Mn layers of a Mn-Nb(110) heterostructure by using a first-principles method. For this study, we use the recently developed Bogoliubov–de Gennes solver for superconducting heterostructures [G. Csire et al., Phys. Rev. B 97, 024514 (2018)] within the first-principles calculations based on multiple scattering theory and the screened Korringa-Kohn-Rostoker Green's function method. In our calculations, we first study the normal-state density of states (DOS) in the single- and double-Mn-layer heterostructures and calculate the induced magnetic moments in the Nb layers. Next, we compute the momentum-resolved spectral functions in the superconducting state for the heterostructure with a single Mn layer and find bands crossing the Fermi level within the superconducting (SC) gap. We also study the SC-state DOS in the single- and double-Mn-layer heterostructures and compare some of our results with experimental findings, revealing secondary gaps, plateaulike regions, and central $\mathsf{V}$-shaped in-gap states within the bulk SC Nb gap that are magnetic order dependent. Finally, we compute the singlet and internally antisymmetric triplet order parameters for each layer for both heterostructures and find an order of magnitude difference in the induced singlet part of the SC order parameter in the Mn layer(s) between the ferromagnetic and antiferromagnetic (AFM) cases in favor of the AFM pairing, with the maximum still being only 4.44% of the bulk Nb singlet order parameter value. We also find a negligible induced triplet part that is, however, comparable to the induced singlet values, indicating some singlet-triplet mixing in the Mn layer(s).

We construct many-body scar states in multiflavor fermionic lattice models that possess strong magnetic or superconducting correlations of a given type specified by a unitary matrix $A$. One of the states maximizes the one-point correlations over the full Hilbert space and has the form of the BCS wavefunction. It may always be made the ground state by adding the correlations as a “pairing potential” to any Hamiltonian supporting group-invariant scars. In our single-flavor, spinful fermion example we consider a superconducting $A$. The BCS scar ground state is a linear combination of the well-known $\eta$-pairing states. In the multiorbital fermion example the BCS ground state maximizes unconventional magnetic correlations. The broad class of eligible Hamiltonians includes many conventional condensed matter interactions. The part of the Hamiltonian that governs the exact dynamics of the scar subspace coincides with the BCS mean-field Hamiltonian. We therefore show that its eigenstates are many-body scars that are decoupled from the rest of the Hilbert space and thereby protected from thermalization. Our results point out a connection between the fields of superconductivity and weak ergodicity breaking (many-body scars) and will hopefully encourage further investigations. They also provide the first feasible protocol to initialize a fermionic system to a scar state in (a quantum simulator) experiment.

The maximum superconducting transition temperature $T_{c,\max }$ in cuprate superconductors exhibits a strong dependence on the number of ${\mathrm{CuO}}_2$ planes $n$ per structural cell, exceeding 100 K in trilayer compounds ($n=3$). Elucidating the mechanism responsible for this enhancement of superconductivity in trilayer systems is therefore a central issue. Here we investigate the quasiparticle dynamics of optimally doped Bi-based cuprates ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{Ca}}_{n-1}{\mathrm{Cu}}_n{\mathrm{O}}_{2n+4+\delta }$ ($n=1–3$), using time-resolved pump-probe reflectivity measurements, with particular focus on the trilayer Bi2223 ($n=3$). In all compounds, the transient reflectivity reveals two characteristic components: a slow superconducting (SC) response and a fast pseudogap (PG) response with opposite signs under our probe conditions. These responses exhibit a distinct and systematic temperature evolution depending on $n$. The photoinduced SC phase depletion energy densities $U_d^{\mathrm{SC}}$ for all three compounds follow a universal scaling with $T_c^2$, whereas the energy density required for PG suppression in Bi2223 is found to be approximately three times larger than the values for La-Bi2201 and Bi2212. These results provide bulk-sensitive evidence that the enhancement of $T_{c,\max }$ in trilayer cuprates is accompanied by a robust pseudogap.

Josephson junctions made of conventional superconductors display Fraunhofer-like oscillations of the critical current as a function of the threaded magnetic flux. When the superconductors are deposited on the surface of a three-dimensional topological insulator, this pattern is slightly modified due to the presence of chiral Majorana modes. Here we calculate the critical current of a Corbino Josephson junction, where the fluxoid becomes quantized and the superconducting phase has an integer winding. We discover that circular junctions exhibit similar behavior in both topologically trivial and nontrivial scenarios, while noncircular junctions demonstrate a remarkable and qualitative distinction. Using a simple analytical model, we show that these noncircular junctions exhibit reentrant superconductivity with a period related to their number of corners and numerically we find that this period is halved in the topological case. The period halving may help establish the existence of topological superconductivity in hybrid topological insulator–superconductor junctions. We find that as long as the circular symmetry of the junction's geometry is broken, the topological junction exhibits a superconducting diode effect with unique properties: the polarity alternates with the parity of the number of fluxes independent of microscopic junction details.

Motivated by the discovery of superconductivity in bilayer ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ at 80 K and the increased superconducting transition temperature, $T_{\text{c}}$, up to 96 K in single crystals of ${\mathrm{La}}_{1.57}{\mathrm{Sm}}_{1.43}{\mathrm{Ni}}_2{\mathrm{O}}_{7-\delta }$ under pressure, we systematically study the effect of Sm substitution on the superconductivity and structure of ${\mathrm{La}}_{3-x}{\mathrm{Sm}}_x{\mathrm{Ni}}_2{\mathrm{O}}_7$ ($0\le x\le 1.5$) under pressure. Experimental investigations in polycrystalline samples reveal that Sm substitution monotonically decreases the lattice constants $c$ and $a$, thereby enhancing crystal structural distortion and leading to an evolution of the metallic ground state in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ to an insulating state in ${\mathrm{La}}_{1.5}{\mathrm{Sm}}_{1.5}{\mathrm{Ni}}_2{\mathrm{O}}_7$. The optimal $T_c^{\text{onset}}$ rises with increasing Sm substitution, and the maximum $T_c^{\text{onset}}$ is 89.2 K in polycrystalline ${\mathrm{La}}_{1.5}{\mathrm{Sm}}_{1.5}{\mathrm{Ni}}_2{\mathrm{O}}_7$. Divergences in $T_c$ compared with single crystals of ${\mathrm{La}}_{1.57}{\mathrm{Sm}}_{1.43}{\mathrm{Ni}}_2{\mathrm{O}}_{7-\delta }$ are likely due to variations in the microstructure induced by different material growth approaches. Our results suggest that the enhancement of $T_c$ in ${\mathrm{La}}_{3-x}{\mathrm{Sm}}_x{\mathrm{Ni}}_2{\mathrm{O}}_7$ is mainly affected by the compressed $c$ lattice before saturation, and the superconducting transition pressure increases with substitution concentration. Our experimental results provide insight into the influence of small-radius rare-earth element substitution on nickelate superconductors, offering a means to further increase the transition temperature.

We propose a general strategy for enhancing the anomalous Nernst coefficient based on the Sommerfeld-Bethe relation. Our formulation expresses the Nernst coefficient in a compact and model-independent form. We show that a large value requires not only a sizable Hall angle but also a pronounced mismatch between the energy dependences (spectral shapes) of the longitudinal and transverse conductivity spectral functions. This perspective provides a transparent explanation for the typically small anomalous Nernst coefficients in simple ferromagnets and yields an explicit optimization criterion. We further present illustrative examples based on simplified spectral-function models designed to highlight how spectral-shape mismatch can strongly enhance the anomalous Nernst coefficient.

We revisit the effective theory for fluctuating spin stripes coupled to a Fermi surface and consider the parameter regime where a spin-nematic phase intervenes between the spin-density-wave state and the symmetric state. It is shown that adding potential disorder to this theory, which acts as an unconventional type of random-field disorder, naturally gives rise to a phase diagram containing a quantum critical point that is described by the universal theory of strange metals with spatial disorder in both the magnitude and sign of the electron-boson coupling term [Patel et al., Science 381, 790 (2023)]. One difference compared with the original theory, however, is that, at nonzero temperatures, the disordered spin-stripe model automatically self-averages over the sign of the coupling. We also study the effects of thermal fluctuations in a phenomenological model for the disordered spin-density-wave state and find from Monte Carlo simulations that a short antiferromagnetic correlation length (order 4–5 lattice constants) already leads to pronounced Fermi arcs in the electronic spectral weight.

We report a comprehensive investigation of the pressure effects on the magnetotransport properties of the topological material ${\mathrm{ZrTe}}_5$ within 1–8 GPa pressure range. With increasing pressure, the characteristic peak ($T_p$) in its electrical resistivity $\rho \left(T\right)$ first shifts to higher temperature and then moves quickly towards the lower temperature before disappearing eventually at 6 GPa. Beyond 6 GPa, the system exhibits metallic behavior across the entire temperature range, and superconductivity emerges below $T_c=1.8\mathrm{K}$ at 8 GPa. Based on the systematic magnetotransport measurement under pressure, we demonstrate that the superconductivity occurs following a significant electronic structure modulation, possibly due to pressure induced structural changes near 6 GPa, which coincides with dramatic enhancement of the magnetoresistance (MR) reaching up to $\sim 1400\%$. Our experimental results are substantiated by density functional theory calculations as the application of pressure drastically alters the density of states near the Fermi level. Notably, multiple hole pockets emerge at the Fermi level from 4 GPa onward, and their contributions are further enhanced with increasing pressure. The combined experimental and theoretical investigation reveals a comprehensive evolution of electronic structure of Dirac semimetal ${\mathrm{ZrTe}}_5$ under pressure and suggest a possible link between the Fermi surface reconstruction in the pressure range of structural transition and the emergence of superconductivity.

Ultrafast control of spin orientations without relying on highly nonequilibrium electron distributions offers a new pathway for femtosecond spintronics. It is shown that excitation of specific vibronic modes can drive a substantial demagnetization of a local moment relative to the magnetization axis, while preserving its total spin quantum number. Using a fully quantum many-body treatment of a local $S=2$ ($d^6$) many-body spin coupled to a driven Jahn-Teller mode with quantum dissipation, we find that the projected spin can be strongly reduced via a Jahn-Teller-induced $xy\uparrow \to yz/zx\downarrow$ transition, which occurs without additional Coulomb exchange cost. The excited state subsequently relaxes back to its original electronic configuration with a rotated spin direction, enabling spin reorientation without generating a large net angular momentum in the electronic subsystem.

An electron beam may experience an anomalous spatial shift during an interface scattering process. Here, we investigate this phenomenon for reflection from mirror-symmetry-protected nodal-ring semimetals, which are characterized by an integer topological charge ${\chi }_h$. We show that the shift is generally enhanced by the presence of nodal rings, and the ring's geometry can be inferred from the profile of shift vectors in the interface momentum plane. Importantly, the anomalous shift encodes the topological information of the ring, where the circulation of the shift vector field ${\kappa }_s$ over a semicircle is governed by the topological charge, with a simple relationship: ${\kappa }_s=-2\pi {\chi }_h$. Furthermore, we demonstrate that the shift and its circulation reflect distinct features of topological phase transitions of the charged rings. This study uncovers a physical signature of topological nodal rings and positions anomalous scattering shifts as a powerful tool for probing topological band structures.

The quantized Hall response of Landau levels (LLs) provides a paradigmatic mechanism for the quantum Hall effect, where successive LLs contribute chiral edge channels. Pseudo Landau levels (pLLs), generated by strain in Dirac materials, faithfully mimic the LL spectrum but are widely believed to be incapable of supporting a quantized Hall conductivity because the associated pseudomagnetic field preserves time-reversal symmetry and the Hall response at the two valleys cancel. A natural question is whether pLLs can induce a quantum Hall effect without requiring a real magnetic field. By introducing a modified Haldane term, we lift the valley degeneracy of the pLL ladders without distorting the pLL quantization. As a result, multiple pLL branches with the same chirality induce a quantized Hall effect with high plateaus at zero magnetic flux. We establish this mechanism using an analytically solvable Fock-state lattice model and demonstrate its robustness in a strained honeycomb tight-binding lattice. Furthermore, we propose a feasible implementation in a cavity quantum electrodynamics platform, where strain and synthetic gauge fields can be programmably engineered.

Chaotic lattice models at high temperature are generically expected to exhibit diffusive transport of all local conserved charges. Such diffusive transport is usually associated with overdamped relaxation of the associated currents. Here we show that by appropriately tuning the interparticle interactions, lattice models of chaotic fermions at infinite temperature can be made to cross over from an overdamped regime of diffusion to an underdamped regime of hot band sound. We study a family of one-dimensional spinless fermion chains with long-range density-density interactions, in which the damping time of sound waves can be made arbitrarily long even as an effective interaction strength is held fixed. Our results demonstrate that underdamped sound waves of charge density can arise within a single band, with strong interactions and far from integrability, and at very high temperature.

Valley photonics has emerged as a promising platform in topological photonic systems, yet the topological nature of valley-dependent phenomena remains unsettled. Theoretically, intervalley scattering may occur with structural imperfections, and global Chern numbers vanish due to time-reversal symmetry. As a result, valley-dependent topology is locally defined around $K\left(K^{\prime }\right)$ points in the half-Brillouin zone (HBZ). While half-integer valley Chern numbers have been widely assumed, their quantization and topological validity remain controversial. Here, we systematically investigate a continuous spectrum of valley photonic crystal designs by evaluating their Berry curvatures, valley Chern numbers, and angular momenta. We show that valley Chern numbers are generically unquantized and instead form a continuous spectrum varying with structural parameters. We further reveal previously unexplored fine structures in the Berry curvature distribution in momentum space. The unquantized valley Chern numbers are attributed to inter- and intravalley cancellation of Berry curvature, highlighting the absence of a protecting mechanism for quantization. Our results call for a reassessment of valley-dependent topology and provide a more rigorous framework for interpreting valley-related photonic phenomena.

The Goos-Hänchen (GH) shift becomes giant in resonant photonic structures, making it promising for refractive index sensors with ultimate sensitivities. Here we provide a complete formalism to analytically describe the GH shift and its associated sensitivity around the critical coupling regime in photonic structures. This analytical framework quantitatively connects physical parameters such as the quality factor, the angular dispersion, the beam size, and the phase singularity to the GH shift. We numerically confirm this theory in two practical designs: a surface plasmon resonance sensor and a Bloch surface wave (BSW) metasurface sensor. Coupling our theory with numerical simulations, we design a BSW metasurface whose GH sensitivity $({10}^{13}\mu \mathrm{m}/\text{RIU})$ is more than 5 orders of magnitude higher than the current state of the art. We also reveal that the main practical limitation to reach ultimate GH sensitivities is the beam size. However, taking into account realistic beam sizes and introducing engineering dispersion for the metasurface, we calculate limits of detection for GH sensors as low as ${10}^{-13}\text{RIU}$ that still surpass current sensors. These results open the way for alternative sensing applications needing high sensitivity and low limit of detection.

Majorana zero modes (MZMs) are non-Abelian quasiparticles with the potential to serve as topological qubits for fault-tolerant quantum computing due to their ability to encode quantum information nonlocally. In multi-Majorana systems configured into two separated subsystems, nontrivial quantum correlations persist, but the presence of trivial Andreev bound states can obscure this nonlocality if MZM preparation fails. To address this, we propose a protocol using an entanglement witness based solely on parity measurements to distinguish the nonlocal characteristics of MZM systems. Our framework is motivated by experimentally relevant parity-measurement architectures and can be implemented in principle, although a full feasibility analysis is left for future work. In a six-site system, the protocol achieves a detection probability of approximately 18% for a matched parity sector. Finally, we present preliminary numerical evidence that the witness retains partial detection power under quasiparticle poisoning, while acknowledging that other imperfections such as intersubsystem overlap remain a serious limitation.

In this work, we investigate the Kitaev honeycomb model employing the recently developed Clifford circuits augmented matrix product states (CAMPS) method. While the model in the gapped phase is known to reduce to the toric code model—whose ground state is entirely constructible from Clifford circuits—we demonstrate that the very different gapless quantum spin liquid (QSL) phase can also be significantly disentangled with Clifford circuits. Specifically, CAMPS simulations reveal that approximately two-thirds of the entanglement entropy in the isotropic point arises from Clifford-circuit contributions, enabling dramatically more efficient computations compared to conventional matrix product state (MPS) methods. Crucially, this finding implies that the Kitaev QSL state retains significant “Clifford-simulatable” structure, even in the gapless phase with non-Abelian anyon excitations when time reversal symmetry is broken. This property not only enhances classical simulation efficiency significantly but also suggests substantial resource reduction for preparing such states on quantum devices. As an application, we leverage CAMPS to study the Kitaev-Heisenberg model and determine the most accurate phase boundary between the antiferromagnetic phase and the Kitaev QSL phase in the model. Our results highlight how Clifford circuits can effectively disentangle the intricate entanglement of Kitaev QSLs, opening avenues for efficiently simulating related and similar strongly correlated models.

In recent years thermoelectric materials have gained attention for electricity generation from waste heat and in cooling applications. However, the efficiency of these materials is still limited, and their improvement is hampered by the complexity of their characterization. The efficiency of these materials is determined by the thermoelectric figure of merit, which depends on their electrical conductivity, Seebeck coefficient, and thermal conductivity. Usually the complete characterization of these properties involves the use of multiple tools, which requires time and introduces uncertainty. Therefore, to boost the discovery of materials with higher efficiency, there is a strong need for fast and accurate experimental characterization. Additionally it is important to measure the thermoelectric properties at the microscale since it enables a thorough understanding of the materials. In this study we present a new method using a micro four-point probe (M4PP) that is able to measure within seconds, at the microscopic scale all of the material properties that define the thermoelectric figure of merit. The method is demonstrated using two skutterudite materials with known thermoelectric properties, and it shows a strong agreement with the reference data. The M4PP method demonstrates potential to revolutionize the testing of thermoelectric materials to expedite their development.

We present a theory of the graphene nanoslide, a fundamental device for graphene straintronics that realizes a single pseudogauge barrier. We solve the scattering problem in closed form and demonstrate that the nanoslide gives rise to a hybrid pseudogauge and electrostatic cavity in the bipolar regime, and hosts one-dimensional transverse channels. The latter can be tuned using a bottom gate between valley-chiral or counterpropagating modes, as well as one-dimensional flatbands. Hence, the local density of states near the barrier depends strongly on the gate voltage with a tunable sublattice and electron-hole asymmetry. In the presence of electron-electron interactions, the nanoslide allows for in situ tuning between a chiral and ordinary Tomonaga-Luttinger liquid.