Collective modes capture the dynamical aspects of fractional quantum Hall (FQH) fluids. Depending on the active degrees of freedom, different types of collective modes can arise in a FQH state. In this work, we consider spinful FQH states in the lowest Landau level (LLL) along the Jain sequence of fillings $\nu =n/(2n\pm 1)$ and compute the Coulomb dispersion of their spin-flip and spin-conserving collective modes in the spherical geometry. We use the LLL-projected density-wave and composite fermion (CF) exciton states as trial wave functions for these modes. To evaluate the dispersion of density-wave states, we derive the commutation algebra of spinful LLL-projected density operators on the sphere, which enables us to extract the gap of the density-wave excitations from the numerically computed density-density correlation function, i.e., the static structure factor, of the FQH ground state. We find that the CF excitons provide an accurate description of the collective modes at all wavelengths, while the density-wave states fail to do so. Specifically, the spin-flip density wave reliably captures the spin-flip collective mode only for the Laughlin and Halperin states, and that too only in the long-wavelength limit. Interestingly, for spin-singlet primary Jain states, the spin-conserving density mode is inaccurate even in the long-wavelength regime. We show that this discrepancy stems from the presence of an additional high-energy spin-conserving parton mode, similar to that found in fully polarized secondary Jain states at $\nu =n/(4n\pm 1)$. We propose an ansatz for this parton mode and compute its Coulomb dispersion in the singlet state at $\nu =2/5$. The predicted parton mode can be observed in circularly polarized inelastic light scattering experiments.

We show how entangled steady states can be prepared by purely dissipative dynamics in a system coupled to a thermal environment. While entanglement is hindered by thermalization when the system and environment exchange a conserved quantity, we demonstrate that breaking this conservation law through the system-environment interaction drives the system to a nonequilibrium steady state. Such an interaction will generate multiple competing equilibration channels, effectively mimicking baths at distinct chemical potentials. When the environment also supports long-range correlations, these channels mediate nonlocal dissipation capable of generating entanglement. We illustrate the scheme in a model of two nitrogen-vacancy (NV) centers weakly coupled to a spin-pumped magnet, where tunable magnon excitations enable steady-state entanglement over finite distances. Our results identify a general mechanism for dissipative entanglement generation, rooted in the conservation structure and environmental correlations rather than fine-tuned coherent control or active driving.

The conventional description of transport through the interface between a normal conductor and a superconductor reduces the system to a one-dimensional problem treating Andreev reflection based on a zero-dimensional Sharvin-type point-contact model, and effectively neglects all considerations of device geometry. While this has been successful in systems where conductance in the normal material is in the diffusive transport regime, such an oversimplification of the problem fails in other transport regimes. In particular, when transport is ballistic as in a typical semiconductor-superconductor hybrid structure, geometrical effects are inherently important, and a proper description must consider a one-dimensional contact injecting into a two-dimensional ballistic cavity. We present a study of this regime and explore the bias-voltage dependence of Andreev transport in a cavity-type device comprised of a high-mobility HgTe quantum well side-contacted by one superconducting and one normal contact, each creating a one-dimensional interface. The enhanced conductance from Andreev transport features two finite-bias conductance peaks, observed at energies within the energy gap of the superconductor. Interestingly, these two peaks respond differently to the application of a perpendicular-to-plane magnetic field. Using a semiclassical model for the quantum transport within the cavity, we are able to attribute each peak to a different class of ballistic trajectories. One class is dominated by normal reflection, and its interference condition is independent of magnetic field, whereas the other one contains retroreflected Andreev processes at the superconductor interface. These create closed trajectories that are strongly suppressed by magnetic field due to Aharonov-Bohm and Doppler shift effects.

The spectral properties, momentum dispersion, and broadening of bulk plasmonic excitations of 26 elemental metals are studied from first principles calculations in the random-phase approximation. Spectral band structures are constructed from the resulting momentum- and frequency-dependent inverse dielectric function. We develop an effective analytical representation of the main collective excitations in the dielectric response, extending our earlier model based on multipole-Padé approximants (MPAs) to incorporate both momentum and frequency dependence [MPA($\mathbf{q}$)]. With this representation, we identify plasmonic quasiparticle dispersions exhibiting complex features, including nonparabolic energy and intensity dispersions, discontinuities due to anisotropy, and overlapping effects that lead to band crossings and anticrossings. Comparing with available experimental data, mainly in the optical limit, we find good agreement with the computed spectra. The results for elemental metals and their effective MPA($\mathbf{q}$) representation establish a reference point that can guide both fundamental studies and practical applications in plasmonics and spectroscopy.

One-dimensional (1D) quantum wires provide a versatile platform for studying strong electron-electron interactions and collective excitations under confinement. Coulomb drag between 1D systems offers a powerful probe of Tomonaga-Luttinger liquid (TLL) physics, with theoretical predictions suggesting a distinct power-law in temperature dependencies between the spin-full and the spin-polarized regimes. However, experimental verification has thus far remained limited. Here, we report measurements of reciprocal and nonreciprocal Coulomb drag between vertically coupled quasi-1D disordered quantum wires in the spin-polarized regime. Clear signatures of spin splitting are observed in both the wires' conductance and in the drag signal. The 1D Coulomb drag signal exhibits different power-law behaviors in the spin-full and spin-polarized regimes and follows the same scaling as predicted for the TLL interaction parameters in ballistic wires. These results are in qualitative agreement with theoretical predictions for backscattering-induced drag in the reciprocal regime of single-subband ballistic quantum wires and show these predictions remain valid in the disordered, nonreciprocal, and multiple-subband regimes.

Evaluation of the quantum lifetime in two-dimensional hole systems, together with band-structure parameters such as the effective mass and $g$ factor, becomes challenging when competing energy scales shape Shubnnikov–de Haas oscillations in a magnetic field. Here, we overcome this challenge for holes with pseudospin $J_{\text{z}}=\pm \frac{3}{2}$, confined in low-disorder strained germanium quantum wells. We extract self-consistently the effective mass, $g$ factor, and quantum lifetime, and estimate a maximum quantum mobility of $133\left(3\right)\times {10}^3{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$, setting a benchmark for holes in group IV semiconductors. The high quality of the hole gas if further highlighted by observing clean fractional quantum Hall states at low magnetic field and density.

The theory of the intrinsic Hall effect, both linear and nonlinear, is rooted in a geometry which is defined in the Bloch-vector parameter space; the formal expressions are mostly derived from semiclassical concepts. When disorder and interaction are considered, there is no Bloch vector to speak of; one needs a more general quantum geometry, defined in a different parameter space. The nonlinear Hall effect is a fundamental geometric response of the many-body ground state, not a band-structure peculiarity. The higher-level geometrical formulation of the intrinsic Hall effect provides very compact expressions, which have the additional virtue—in the Bloch special case—of yielding the known results in a straightforward way: The logic is not concealed by the algebra.

We demonstrate that spin $p\text{−}n$ junctions—magnetic semiconductor homojunctions with spin-splitting-induced band offsets—fundamentally redefine carrier transport via spin-dependent recombination probabilities $r_{\sigma {\sigma }^{\prime }}$. By integrating this mechanism into the Shockley model, we predict a 100 times enhancement in magnetoresistance (MR) sensitivity under small forward bias in the case of large intrinsic spin splitting ($0.1\mathrm{eV}$), where exponential modulation of recombination lifetimes ${\tau }_{\sigma {\sigma }^{\prime }}$ by magnetic fields amplifies resistance changes. The MR in our model exhibits a strong dependence on the intrinsic spin-splitting energy, showing a marked enhancement with increasing splitting magnitude. Angular momentum conservation enables magnetically tunable circularly polarized luminescence: Exclusive conduction band or valence band splitting in both neutral regions achieves near-half polarization ($|P_I|\approx 50\%$), while global splitting degrades emission coherence. Furthermore, we propose a “spin Zener filter” exploiting $\sim 1\text{eV}$ valence band splitting in (Ga, Mn)As, where spin-dependent barrier heights generate near 100% spin-polarized tunneling currents within a voltage-selective window. Our extended model incorporating $p$-orbital effects reveals that while the orbit minimally affects the current magnitude, it dramatically alters the circular polarization degree of the luminescence. This significant difference arises primarily from the selection rules $\mathrm{\Delta }m=\pm 1$ imposed by the $p$-orbital character. These results establish spin $p\text{−}n$ junctions as a universal design paradigm for magnetically amplified electronics, polarization-programmable optoelectronics, and voltage-gated spin injection without ferromagnetic contacts.

The structures and properties of two-dimensional (2D) materials are profoundly governed by the interlayer coupling and stacking configuration. In particular, interlayer sliding can drive structural phase transitions and give rise to novel quantum phenomena in 2D materials. Here, we report a high-pressure study of structural and electronic properties in $\mathrm{N}{\mathrm{b}}_{0.6}\mathrm{R}{\mathrm{e}}_{0.4}\mathrm{S}{\mathrm{e}}_2$ up to 60.2 GPa. The synchrotron X-ray diffraction reveals a first-order isosymmetric structural transition from the $2H_c$ to the $2H_a$ phase near 16.4 GPa, driven by interlayer sliding. Concomitantly, a new Raman phonon mode ($M_1$) occurs at a critical pressure $P_c$ around 14.3 GPa and exhibits an anomalous redshift with increasing pressure, signaling substantial lattice softening. Superconductivity is observed at $P_c$, with a critical temperature $T_c$ of $\sim 4.4\mathrm{K}$. Strikingly, $T_c$ displays a notable nonmonotonic behavior, characterized by a prominent dome followed by a slow enhancement at higher pressures. We attribute the initial dome to the combined effects of phonon softening and a Lifshitz transition, while the reentrant enhancement of the superconducting phenomenon at higher pressures is closely associated with the evolution of carrier concentration, as evidenced by Hall effect measurements. Our results underscore interlayer sliding as a crucial mechanism for modulating electronic properties and suggest new avenues for realizing exotic superconducting states in 2D materials.

Using constrained-path quantum Monte Carlo simulations on a bilayer two-orbital Hubbard model, we systematically investigate the pairing symmetry competition in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. Our findings reveal that Hund's coupling $J_H$ and crystal field splitting $\mathrm{\Delta }E$ are the key factors controlling the ground-state pairing symmetry. Increasing either $J_H$ or $\mathrm{\Delta }E$ robustly enhances the interlayer $s_{\pm }$-wave pairing, driven by interlayer antiferromagnetic correlations, while simultaneously suppressing the intralayer $d$-wave pairing, which is mediated by intralayer antiferromagnetic spin fluctuations. In the physically relevant parameter regime for ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, the $s_{\pm }$-wave emerges as the dominant pairing symmetry. Crucially, this robust $s_{\pm }$-wave pairing persists even when the $\gamma$ pocket is absent, providing theoretical support for the recent experimental observations of high-temperature superconductivity in thin films.

The recently reported gate-tunable superconductivity in monolayer ${\mathrm{WTe}}_2$ [Science 362, 922 (2018); Science  362, 926 (2018); Nat. Phys. 20, 269 (2024); Phys. Rev. Res. 7, 013224 (2025)] exhibits several striking anomalies beyond the standard paradigm, including a contrasting carrier-density dependence of the transition temperature $T_c$ in weakly and strongly disordered regimes, and more surprisingly, the sudden disappearance of superconducting fluctuations below a critical carrier density. To understand these features, we go beyond mean-field theory and develop a microscopic framework that treats the gap and superfluid density by explicitly and self-consistently incorporating both Nambu-Goldstone (NG) phase fluctuations and Berezinskii-Kosterlitz-Thouless (BKT) fluctuations. We show that these fluctuations are minimal in the weak-disorder regime but become crucial under strong disorder, where the zero-temperature gap renormalized by NG quantum fluctuations becomes density-dependent while the BKT fluctuations drive the $T_c$ below the gap-closing temperature. Simulations within this unified framework combined with the density-functional-theory input to account for the excitonic instability quantitatively reproduced nearly all key experimental observations, providing a consistent understanding of reported anomalies.

Quantum thermometry plays a critical role in the development of low-temperature sensors and quantum information platforms. In this work, we propose and analyze a hybrid circuit quantum electrodynamics architecture in which a superconducting qubit is dispersively coupled to two distinct bosonic modes: one initialized in a weak coherent state as a phase reference and information buffer and the other coupled to a thermal environment. We show that the qubit serves as a sensitive readout of the probe mode, mapping the interplay between thermal and coherent photon-number fluctuations onto measurable dephasing. This coherence-mediated mechanism enables improved sensitivity to thermal energy fluctuations in the sub-millikelvin regime through Ramsey interferometry. We derive analytic expressions for the probe coherence envelope, compute the quantum Fisher information for temperature estimation, and demonstrate numerically that the presence of a coherent reference enhances the qubit's sensitivity to small changes in thermal photon occupancy. Our results establish a coherence-enabled approach to thermometry and provide a scalable platform for future calorimetric sensing in high-energy physics and quantum metrology.

Chiral phonons have been identified in several chiral crystals, primarily in crystals with trigonal symmetry and threefold screw axes. In this study, chiral phonons in ${\mathrm{CrSi}}_2$, a chiral crystal with a sixfold helical structure, were investigated. Circularly polarized Raman spectroscopy revealed a subtle splitting of doubly degenerate $E_2$ phonon modes between cross-circular polarization configurations. These observations, supported by first-principles phonon calculations, indicate the presence of chiral phonons in ${\mathrm{CrSi}}_2$, expanding the scope of materials that exhibit chiral vibrational modes beyond the conventional trigonal class.

We propose a pair spin-orbit interaction mechanism by establishing a mesoscopic many-particle Rashba Hamiltonian. In lowest order, this Hamiltonian self-consistently describes exciton spin relaxation in monolayer transition metal dichalcogenides (TMDC) due to local electric fields caused by spatial asymmetries in the dielectric environment. For a monolayer ${\mathrm{MoSe}}_2$ on a sapphire or ${\mathrm{SiO}}_2$ substrate above 77 K showing a bright-dark splitting in the meV range, the local electric field causes fast intravalley spin relaxation on a sub-picosecond time scale, whereas it is negligible for other TMDCs with larger bright-dark splitting.

We investigated the structural and magnetic properties of single-crystalline ${\mathrm{VCl}}_3$, a newly synthesized member of the vanadium trihalide family. High-quality single crystals were grown by the chemical vapor transport method, and their behavior was characterized using neutron diffraction and thermodynamic measurements. We show that ${\mathrm{VCl}}_3$ crystallizes in the ${\mathrm{BiI}}_3$-type structure at room temperature and undergoes a structural phase transition at $T_S=103.7\left(5\right)\mathrm{K}$ that lowers the lattice symmetry, followed by a zigzag antiferromagnetic order with a propagation vector $k=(0,0.5,1)$ below $T_N=21.8\left(1\right)\mathrm{K}$. Neutron diffraction experiments indicate that the ordered moments are canted by approximately ${21}^{\circ }$ away from the $c$ axis toward the $a$ axis, yielding a total moment of approximately $1.09\left(2\right){\mu }_{\mathrm{B}}/{\mathrm{V}}^{3+}$. Field-dependent magnetization along the $c$ axis exhibits a half magnetization plateau, indicative of a field-stabilized fractional state. These results establish ${\mathrm{VCl}}_3$ as a new platform for exploring structural transitions, anisotropic magnetism, and field-induced phases in vanadium-based honeycomb magnets.

We show that a small charged probe near a spherical topological insulator causes the latter to rotate around a symmetry axis defined by the center of the sphere and the position of the charge outside the latter. The rotation occurs when the distance from the charge to the center of the sphere is changed. This phenomenon occurs due to induced static fields and is a consequence of the axion electrodynamics underlying the electromagnetic response of a topological insulator. Assuming a regime where the charged probe can be regarded as a point charge $q=Ne$, where $N$ is a positive integer and $e$ is the elementary electric charge, we obtain that the rotation frequency is given by $\omega ={\left(N\alpha \right)}^2\mathrm{{\rm Y}}(\epsilon ,d/a)/I$, where $I$ is the moment of inertia, $\alpha$ is the fine-structure constant, and the function $\mathrm{{\rm Y}}$ depends on the dielectric constant $\epsilon$ and the relative distance $d/a$ of the charge from the center of the sphere of radius $a$. Since the point charge also induces Hall currents on the surface, we also compute their associated angular momentum. This allows us to derive an exact expression for the electronic velocity on the surface as a function of $a/d$.

We study the interplay of magnetic order and superconductivity in the square-lattice Hubbard model under periodic driving with circularly polarized light. Formulating diagrammatic techniques based on the random-phase approximation in terms of Floquet Green's functions, allows us to analyze fluctuation-driven unconventional pairing for weak to moderate interactions. The interplay of repulsive interactions and photoassisted hopping of electrons gives rise to a rich magnetic phase diagram featuring an antiferromagnetic-to-ferromagnetic transition prior to a Floquet Lifshitz transition. Close to the antiferromagnetic transition, topological $d+id$-wave superconductivity prevails in the phase diagram for a wide range of drive parameters. At intermediate- to high-frequency driving near the Floquet Lifshitz transition, superconducting orders are tuned from spin-singlet $d$-wave to spin-triplet $p$-wave character, providing an effective protocol for Floquet engineering topological superconductivity.

The ${\mathrm{NV}}^{-}$ color center in diamond has been demonstrated as a nanoscale sensor for quantum metrology. However, the properties that make it ideal for measuring, e.g., minute electric and magnetic fields, also make it sensitive to imperfections in the diamond host. In this work, we quantify the impact of nearby native defects on the many-body states of ${\mathrm{NV}}^{-}$. We combine previous quantum embedding results of strain and electric-field susceptibilities of ${\mathrm{NV}}^{-}$ with density functional theory calculations on native defects. The latter are used to parametrize continuum models in order to extrapolate the effects of native defects up to the micrometer scale. We show that under ideal measuring conditions, the optical properties of ${\mathrm{NV}}^{-}$ are measurably affected by the strain caused by single carbon interstitials and vacancies up to 200 nm away; further, the ${\mathrm{NV}}^{-}$ is measurably affected by the electric field of such charged (neutral) native defects within a micron (100 nm). Finally, we show how measuring multiple individual ${\mathrm{NV}}^{-}$ centers in the vicinity of a native defect can be used to determine the nature of the defect and its charge state.

Spin-triplet superconductivity is an intriguing quantum coherent state with both spin and orbital degrees of freedom, which holds significant potential for future applications in quantum technology. However, how the spin of the triplet pairs responds to an external magnetic field remains poorly understood. This is mainly due to the absence of suitable spin-triplet superconductors. Here, we report results of Knight-shift and ac-susceptibility measurements on ${\mathrm{UTe}}_2$. We demonstrate that the spin susceptibility, which slightly decreases compared to the normal-state value below the superconducting (SC) transition temperature $T_{\mathrm{c}}$, is rapidly restored and nearly recovers to the normal-state values around 5 T, well below the SC upper critical field $H_{c2}$ when the magnetic field is applied along the $c$ axis ($H\parallel c$). In addition, we found that $H_{\mathrm{c}2}$ of superconductivity becomes larger when the SC spin aligns with the magnetic field. By considering the results on $H\parallel b$, our results suggest the presence of a close relationship between the spin configuration of the triplet pair and $H_{\mathrm{c}2}$, as well as the anisotropic pinning interaction acting on the triplet pairs. These phenomena, which have never been observed in spin-singlet superconductors, represent characteristic features unique to spin-triplet superconductors. We discuss the similarities between superconductivity in ${\mathrm{UTe}}_2$ and superfluid ${}^3\mathrm{He}$, focusing on their spin-triplet pairing states.

Noncentrosymmetric superconductors, characterized by broken inversion symmetry, represent a distinctive subclass of unconventional superconductors. Here, we report the growth of single crystals of a noncentrosymmetric superconductor $h$-NbS, and systematical characterization of crystal structure and superconducting properties. Different from $o$-NbS, $h$-NbS crystallizes in a NiAs-type hexagonal superstructure with site-selective Nb vacancies. First-principles calculations reveal that the $\mathrm{Nb}\text{−}4d$ states dominate at the Fermi level ($E_{\mathrm{F}}$), with the density of states near $E_{\mathrm{F}}$ manifesting significant sensitivity to the concentration of the Nb vacancies. Nodeless moderately coupled two-gap superconductivity with a critical temperature of 2.6 K is confirmed in this strong type-II superconductor. The anisotropic parameters based on upper and lower critical fields have small values of $\sim 1.4$ and $\sim 1.3$, respectively, which demonstrate that the Cooper pairs show almost isotropic resilience to magnetic field. We surprisingly note that the upper critical field along the $ab$ plane surpasses the Pauli limit, largely arising from the two-dimensional Fermi-surface sheet around the K and H points of the Brillouin zone, which is related to the breaking of inversion symmetry. In contrast to quasi-one-dimensional and quasi-two-dimensional Nb-chalcogenide superconductors, the three-dimensional $h$-NbS featuring Pauli-limit violation provides a unique material for investigating unconventional superconductivity.