One efficient mechanism for generating a charge supercurrent is Andreev reflection, in which the electric current injected from a normal metal into a conventional superconductor (SC) is converted into a supercurrent, thereby preserving charge conservation. Here, we propose a general principle for generating spin supercurrents in unitary (equal-spin) triplet SCs by analogy with such charge transport, i.e., assuming spin conservation. We find a spin torque that is proportional to the triplet superconducting order parameter and, in the spin-conservation scenario, converts the particle spin to that of Cooper pairs. Based on this general principle, we propose an implementation to efficiently generate a spin supercurrent in unitary triplet SCs, even though the condensate carries no spin polarization at equilibrium, by the magnetization dynamics $\mathbf{M}\left(t\right)$ of a proximity magnetic nanostructure. In this process, the quasiparticle spin current is also efficiently generated. The efficiency of spin pumping of both Cooper pairs and quasiparticles is not solely limited to the $d\mathbf{M}/dt\times \mathbf{M}$ due to the emergent particle-hole symmetry, thereby going beyond the conventional spin pumping of electrons. This general principle provides an efficient approach to generating and manipulating dissipationless spin currents in many unconventional SCs.

This work addresses a frequently overlooked aspect of one-dimensional non-Hermitian multilayered systems: the distinction between modal and operational non-Hermitian responses. While the scattering matrix is commonly used to identify special operational regimes in non-Hermitian systems, the full-state transfer matrix provides a more comprehensive view of both internal and external system dynamics. Here, we systematically explore the behavior of the full-state transfer matrix in non-Hermitian multilayers and we moreover examine how the special case of parity-time (PT) symmetry shapes modal phase response and influences transmission and reflection properties. We establish a complete mathematical framework and further elucidate, through a series of representative examples, the differences between scattering/wave transfer-matrix and full-state transfer matrix eigenvalue spectra and PT-phase criteria, uncovering patterns that inform both design and theoretical understanding. Our results demonstrate the full-state transfer matrix as a versatile tool for analyzing non-Hermitian multilayers, with potential applications in linear optics, impedance characterization, and tunable photonic systems.

We report the magnetic dynamics of as-deposited $\mathrm{M}{\mathrm{n}}_2\mathrm{Au}/\mathrm{CoFeB}$ heterostructures via time-resolved magneto-optical Kerr effect spectroscopy. Increasing the pump fluence from 5 to $25\mathrm{mJ}/\mathrm{c}{\mathrm{m}}^2$ results in an effective demagnetization field $4\pi M_{\text{eff}}$ decreasing from 9.178 to 7.483 kOe, accompanied by magnetic damping ${\alpha }_0$ decreasing from 0.0225 to 0.0110. The concomitant modulation of $4\pi M_{\text{eff}}$ and ${\alpha }_0$ is elucidated through the mechanism that the pump excitation with elevated fluence suppresses the antiferromagnetic (AFM) order of $\mathrm{M}{\mathrm{n}}_2\mathrm{Au}$ and antiferromagnetic-ferromagnetic (AFM-FM) exchange coupling by thermal effect, thereby reducing both $4\pi M_{\text{eff}}$ and ${\alpha }_0$. These findings provide critical insights into femtosecond laser-modulated magnetic dynamics of AFM/FM bilayers and pave the way for AFM/FM applications in spintronics.

Skyrmion crystals have been primarily discovered under a magnetic field for materials with noncentrosymmetric interactions. More recent developments have investigated the stability of skyrmion crystals in itinerant magnets without a magnetic field. In this study, we find that a type of skyrmion crystal with two topological charges per unit cell and no magnetization at the ferromagnetic point in reciprocal space, SkX-2, is naturally stabilized in an $\mathrm{SO}\left(3\right)$-symmetric model with short-range interactions realized by the Heisenberg model on the triangular lattice with scalar chirality. We complement our numerical results with a theoretical analysis that quantitatively describes the transition from the ferromagnetic to the SkX-2 ground state and the evolution of the topological charge density. Despite the constraints given by the Mermin-Wagner theorem at finite temperature, the SkX-2 can either exhibit a first-order phase transition with translation symmetry breaking, or a continuous transition to a floating solid depending on the charge density, which is given by the strength of the scalar chirality interaction. Finally, the numerical results indicate the presence of ${\mathbb{Z}}_2$-vortices at finite temperature above the tetrahedral ground state in the antiferromagnetic region of our model, suggesting the existence of a vortex topological transition similar to that reported in the ordering of the pure antiferromagnetic model.

We investigate the fidelity susceptibility, which quantifies the sensitivity of single-particle eigenstates to perturbations, in the three-dimensional Anderson model. As a function of disorder strength $W$, it exhibits two distinct peaks. The first peak signals a crossover at weak disorder strength from plane-wave states to single-particle quantum chaos, and its position shifts toward $W\to 0$ in the thermodynamic limit. The second peak emerges, to high numerical accuracy, at the critical disorder strength associated with the Anderson localization transition. We further show that the divergence of the first peak is maximal, scaling as the square of the inverse frequency cutoff, whereas the divergence of the second peak is submaximal. We relate the latter suppression to the fractal structure of single-particle eigenstates at criticality. We discuss two distinct scenarios that give rise to the peaks in the fidelity susceptibilities. Moreover, studying the scaling of typical fidelity susceptibilities above the Anderson transition, we find evidence of two distinct regimes of nonergodic behavior.

Spin transport in magnetic insulators is often treated by assuming that magnons carry a fixed spin angular momentum of $\hslash$, which does not hold in general, however. Here, we calculate the magnon spin angular momentum of a layered antiferromagnet as a function of applied magnetic field and wave vector. We show that the triaxial anisotropy and intralayer dipolar interactions in bilayer CrSBr renormalize the magnon spin angular momentum, which diverges upon field-induced magnon softening. This divergence gives rise to a pronounced peak in the thermal spin Seebeck response and provides a clear spin-caloritronic signature of soft magnons.

The low-pressure phase diagram of ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ provides an important reference for understanding its pressure-induced high-temperature superconductivity. While the spin-density-wave transition at $T_{\text{SDW}}\approx 150\mathrm{K}$ is increasingly well established, the origin of the second density-wave transition at $T_{\text{DW}}\approx 130\mathrm{K}$ has remained unresolved. Here, we perform unrestricted Hartree-Fock calculations to investigate the potential origin of the second transition. Within the orthorhombic phase, the degeneracy between possible ordering wave vectors at ${\mathit{Q}}_Y=(0,\pi )$ and at ${\mathit{Q}}_X=(\pi ,0)$ is lifted and the electronic system develops a double-stripe spin-density wave with ordering vector ${\mathit{Q}}_Y=(0,\pi )$. We identify that the pure double-stripe spin state is unstable in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ towards a commensurate charge-density wave instability, which favors a spin-modulated double-stripe order with intertwined charge and spin instabilities and establish the hierarchy of ordered states in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. We further discuss our results in the context of available experimental literature and propose further experimental tests to elucidate the origin of the SDW/DW states in this system.

Neutral-atom quantum simulators provide a powerful platform for realizing strongly correlated phases, enabling access to dynamical signatures of quasiparticles and symmetry breaking processes. Motivated by recent observations of quantum phases in flux-frustrated ladders with nonvanishing ground-state currents, we investigate interacting bosons on the dimerized Benalcazar-Bernevig-Hughes (BBH) lattice in two dimensions—originally introduced in the context of higher-order topology. After mapping out the phase diagram, which includes vortex superfluid (V-SF), vortex Mott insulator (V-MI), and featureless Mott insulator (MI) phases, we focus on the integer filling case. There, the MI/V-SF transition breaks the ${\mathbb{Z}}_2^T$ and U(1) symmetries, where ${\mathbb{Z}}_2^T$ corresponds to time-reversal symmetry (TRS). Using a slave boson description, we resolve the excitation spectrum across the transition and uncover a chiral Higgs mode whose mass softens at criticality, providing a dynamical hallmark of emergent chirality that manifests via the oscillation of the loop currents in quench dynamics. Our results establish an experimentally realistic setting for probing unconventional TRS-broken phases and quasiparticles with intrinsic chirality in strongly interacting quantum matter.

Recent experiments with nanopatterned thin films revealed an unusual quantum superconductor to metal phase transition (QSMT) with a linear-in-temperature resistivity. In contrast, most known examples of such transitions and standard theoretical considerations predict a temperature-independent sheet resistance of order $R_Q=\hslash /e^2$. We propose an effective theory of a disordered superconductor which features a QSMT with robust $T$-linear resistivity at the critical point. The crucial ingredient in our model is spatial disorder in the pairing interaction. Such random pairing mirrors the emergent phase disorder seen in a recent mean-field study of a microscopic $d$-wave superconductor subject to potential disorder. We also make the prediction that in such systems the diamagnetic susceptibility diverges as $ln\mathrm{\Lambda }/T$, which starkly differs from the power-law divergence in standard XY transitions.

Understanding how the interaction range and various types of disorder affect the level statistics of many-body quantum systems, leading to the emergence of many-body localization (MBL), is a challenging open frontier. We study the level statistics of a variant of the spin-$1/2$ Haldane-Shastry model with $1/r^{\alpha }$ interactions, where $\alpha \ge 0$ parametrizes the range of the interactions, in the presence of position disorder and/or random magnetic fields. We find that neither position disorder nor random magnetic fields alone yields pristine Poisson statistics in this system; however, Poisson statistics emerge in their combined presence, suggesting the emergence of MBL when both types of disorder coexist. Interestingly, once random magnetic fields break the $SU\left(2\right)$ symmetry, the strength of the position disorder, $\delta$, appears to play an important role, as evidenced by an approximate scaling collapse of the disorder-averaged gap ratios that is parametrized in terms of a single parameter, $\alpha \delta$.

Tuning the chemical potential of a solid to the vicinity of a Van Hove singularity (VHS) is a well-established route to discovering emergent quantum phases. In monolayer graphene, the use of electron-donating metal layers has recently emerged as a method to dope the chemical potential to the nearest VHS, as evidenced by Angle-Resolved Photoemission Spectroscopy (ARPES) measurements. In this work, we study the spatial uniformity of the doping from this process using spectroscopic imaging scanning tunneling microscopy (SI-STM). Using molecular beam epitaxy, we achieve electron doping of graphene on silicon carbide using Ytterbium (Yb-Graphene). We show using in situ ARPES that the chemical potential is shifted to within 250 meV of the VHS. Using insitu SI-STM, we establish that there exists significant inhomogeneity in the VHS position in overdoped graphene. We find two separate reasons for this. First, the spatial inhomogeneity of the intercalated Yb leads to local variations in the doping, with a length scale of inhomogeneity set by the screening length of $\sim 3$ nm. Second, we observe the presence of substitutional Yb dopants in the graphene basal plane. These Yb dopants cause a strong local shift of the doping, along with a renormalization of the quasiparticle amplitude. Theoretical calculations confirm that the Yb impurities effectively change the local potential, thus energetically shifting the position of the Van Hove singularity. Our results point to the importance of considering the spatial structure of doping and its inextricable link to electronic structure.

Van Hove singularities (VHSs) play a pivotal role in driving correlated electronic phenomena. Traditional classifications focus only on critical points where the band gradient vanishes in all directions. Here we establish a unified classification of VHSs in three-dimensional systems, characterized by the number of vanishing gradient components and Hessian eigenvalues: ordinary $\left(M\right)$, higher-order $(T_1$, $T_2$, $T_3)$, noncritical ordinary $(N_0$, $N_1$, $N_2)$, and noncritical higher-order $(S_1$, $S_2)$ types. Noncritical VHSs exhibit directional quenching: The gradient vanishes in a two-dimensional subspace while remaining finite along the orthogonal direction, yielding finite density-of-states enhancements with distinct energy dependences. Using an $s$-orbital tight-binding model on the pyrochlore lattice with spin-orbit coupling, we demonstrate that all singularity classes emerge at distinct high-symmetry points through controlled tuning of the hopping ratio. This work establishes directional criticality and higher-order flatness as design principles for tailoring density-of-states enhancements in three-dimensional quantum materials.

We present a comprehensive computational study of driven quantum dot arrays in a square lattice configuration subject to an external magnetic field and coupled to a cylindrical far-infrared photon cavity. The driving is introduced through a harmonic modulation of the full electron-photon interaction, therefore including both paramagnetic and diamagnetic contributions. The electron-electron Coulomb interactions are treated within density functional theory, while the electron-photon coupling is modeled using a many-body configuration interaction approach at each iteration of the density functional. By exploiting the unique properties of the cylindrical ${\mathrm{TE}}_{011}$ cavity mode, we demonstrate selective enhancement of diamagnetic two-photon transitions. Our results reveal that the effectiveness of harmonic modulation of the electron-photon interaction is strongly dependent on both the driving frequency and the electron occupation number per dot. When the driving frequency approaches twice the cavity photon frequency, the system exhibits resonant behavior characterized by efficient photon pumping, occupation of higher-order photon replicas, and activation of collective radial Coulomb breathing modes. These findings establish a controllable mechanism for manipulating photon states in coupled quantum dot-cavity systems and provide insights into the interplay among harmonic modulation, photonic excitations, magnetic confinement, and many-body electron correlations in dimensionally reduced nanostructures.

Flat bands underlie a diverse range of quantum phenomena, from strongly correlated phases to superconductivity. We theoretically establish that a two-dimensional electron gas under a linear magnetic-field gradient and a transverse electric field exhibits electrically tunable flat bands. When the electric field magnitude is tuned to a value within a discrete sequence, these bands become strictly dispersionless. By providing exact classical and quantum solutions, we demonstrate that these states are high-order Landau levels associated with drift-compensated cyclotron orbits of carriers arising from the synergy between the magnetic-field gradient and the electric field. These electrically controllable Landau levels exhibit quantized Hall conductance and a strongly enhanced density of states. Our results provide a route for flat-band creation, magnetoelectric band engineering, and quantized Hall currents controlled via source-drain voltage.

We predict a supercurrent-driven Néel spin-orbit torque in a superconductor/$d$-wave altermagnet heterostructure, associated with the emergence of spin-triplet correlations. The effect can be understood as a consequence of the supercurrent-induced spin polarization, owing to the interplay between spin-orbit coupling and momentum-dependent spin splitting, as found, for example, in altermagnets. Remarkably, the supercurrent can be tuned by the Néel-vector direction, and the supercurrent-induced torque can both propel magnetic domain walls and reverse the Néel-vector orientation within a domain wall. These findings establish superconductor/altermagnet heterostructures as a versatile platform for the supercurrent-driven control of the Néel vector, with potential applications in racetrack memory, dissipationless superconducting electronics, and unconventional computing.

We report time-resolved optical pump-terahertz third-harmonic generation spectroscopy of picosecond nonthermal many-body charge dynamics in high-purity silicon at room temperature. Although in thermal equilibrium excitons in silicon are unstable due to a lower binding energy than the thermal energy at room temperature, following pulsed nonresonant optical pumping we can identify the formation of transient excitonic states on the picosecond timescale in our high-resolution nonlinear spectroscopic measurements. In contrast to unbound electron-hole pairs, the nonthermal many-body excitonic dynamics feature a characteristic time-dependent evolution, a distinct dependence on charge density, and a nonperturbative nonlinear terahertz response.

The crystal structure, vibrational spectra, and magnetic structure of the quasi-two-dimensional layered van der Waals antiferromagnet CrSBr were studied by means of x-ray diffraction (XRD) and Raman spectroscopy at high pressures up to 33 GPa and ambient temperature and neutron diffraction (ND) up to 5.7 GPa in the temperature range 10–300 K. The orthorhombic crystal structure with Pmmn symmetry observed at ambient pressure remains stable at pressures up to 8 GPa according to the XRD and Raman data. At ambient pressure, $A$-type antiferromagnetic (AFM) order is formed in the initial orthorhombic phase below $T_{\mathrm{N}}=133\mathrm{K}$. Application of high pressure leads to a suppression of the $A$-type AFM order. The Néel temperature decreases sharply by 30% to 93 K, and Cr ordered magnetic moment values are reduced from $3.1{\mu }_{\mathrm{B}}$ to $2.0{\mu }_{\mathrm{B}}$ in the pressure range 0–5.7 GPa, as found in the ND experiments. The effects of pressure-controlled compressive intralayer biaxial lattice strain and interlayer uniaxial lattice strain along the $c$ axis on the magnetic state of CrSBr are analyzed. The evaluated relationship between the variation of the biaxial lattice strain and observed modification of the $T_{\mathrm{N}}$ value via the tuning of structural parameters points to its important role in the tuning of magnetic properties. Upon further compression, a complex sequence of structural phase transitions at $P_1\sim 8, P_2\sim 16$, and $P_3\sim 28\mathrm{GPa}$ was detected by the XRD and Raman measurements. The first possible phase transition at $P_1\sim 8\mathrm{GPa}$ is accompanied by anomalies in the pressure behavior of lattice parameters and softening of the lowest-frequency vibrational mode with $A_{\mathrm{g}}$ symmetry. The second phase transition at $P_2\sim 16\mathrm{GPa}$ is associated with the appearance of the ($\frac{1}{2}01$) superstructure peak in the XRD spectra and extra modes in Raman spectra, pointing to the formation of a structural modification with the supercell doubled along the $a$ axis. The third phase transition at $P_3\sim 28\mathrm{GPa}$ is accompanied by the disappearance of the superstructure peak in the XRD spectra, implying a breakdown of the supercell back to the initial cell geometry. All the observed phases of CrSBr demonstrate pseudo-orthorhombic character, and they are structurally similar, according to the XRD data. The possible appearance of a subtle monoclinic distortion in the high-pressure phases cannot be excluded due to the observation of extra Raman modes above the $P_2$ and $P_3$ transition pressures. The present experimental information is important for further clarification of possible microscopic mechanisms for controlling the magnetic states of CrSBr and relevant van der Waals materials through the application of high external pressures or strain engineering.

The discovery of infinite-layer nickelate superconductors has generated great enthusiasm for exploring new nickelate superconductors with higher $T_{\mathrm{c}}$ and further elucidating their superconducting mechanism. In this work, we systematically investigate the pressure effect on both the normal state and superconductivity of ${\mathrm{La}}_{0.8}{\mathrm{Sr}}_{0.2}{\mathrm{NiO}}_2$ thin film by measuring resistance under various hydrostatic pressures up to 7.5 GPa. The results show that $T_{\mathrm{c}}$ exhibits a monotonic increase from $T_{\mathrm{c}}^{\mathrm{onset}}\sim 19$ K at ambient pressure to $T_{\mathrm{c}}^{\mathrm{onset}}\sim 26$ K at 7.5 GPa. Moreover, normal-state resistance displays linear behavior in the measured pressure range, which is a hallmark of the strange metal state. The constructed temperature-pressure phase diagram reveals a potentially universal linear enhancement of $T_{\mathrm{c}}$ in infinite-layer nickelate superconductors at nearly optimal doping. This indicates that the evolution of $T_{\mathrm{c}}$ can be affected by multiple factors and can be further enhanced by pressure, epitaxial stress, or substitution of rare-earth metals. Our work provides critical insights for further enhancing $T_{\mathrm{c}}$ and constructing theoretical models to explore the superconducting mechanism in infinite-layer nickelate systems.

Transition metal dichalcogenides (TMDs) hold relevance for spin-triplet superconducting phases due to their inherent Ising spin-orbit coupling, but the majority of studies have so far focused on oversimplified models. In this work, we consider a TMD monolayer using a three-orbital model with anisotropic couplings and investigate the emergent superconducting properties when it is placed in proximity to a conventional spin-singlet $s$-wave superconductor. We find that the multiorbital nature of the TMDs lead to superconducting gaps not only at zero energy but also at higher energies, so-called hybridization gaps, which exhibit a complex structure due to the anisotropic couplings, challenging their spectral measurement. Moreover, we find that the inherent Ising spin-orbit coupling induces a spin splitting and a spin polarization along the $z$ direction, which correlates with the emergence of mixed spin-triplet superconducting pairs. These spin-triplet pair correlations appear in the monolayer as a proximity-induced effect due to the impact of the Ising spin-orbit field on conventional spin-singlet $s$-wave superconductivity. Taking realistic parameters for a ${\text{MoS}}_2$ monolayer, we show that the Ising field is strong enough to induce spin-triplet pair correlations of the same magnitude as their spin-singlet counterparts. We also include Rashba spin-orbit coupling, naturally emerging in a heterostructure and find that it induces equal spin-triplet superconducting pairs that compete with the mixed spin-triplet pairs induced by the Ising spin-orbit coupling. Our findings help understand the superconducting properties of TMDs in proximity to conventional superconductors.