Boron's electron deficiency favors multicenter bonding and enables planar or quasiplanar boron nanostructures with unusually stable pristine edges and corners. Yet a compact bonding picture that explains these stability trends remains elusive. Here we introduce a bonding model for triangular-lattice-based planar boron clusters, defined by four bonding rules that use only 3c-2e and 2c-2e bonding and σ bond resonance. The model allows intuitive construction of σ bonding configurations without extensive quantum calculations, revealing the origin of the high stability of planar boron clusters and rationalizing their effective self-termination at pristine edges and specific corners. From this model we extract three stability criteria: energetically favored clusters tend to have (i) obtuse-angle convex and/or concave corners, (ii) flat edges with an even number of atoms, and (iii) an increasing number of hexagonal holes as the cluster grows. Applying these criteria, we predict ${\mathrm{B}}_{49}, {\mathrm{B}}_{70}$, and ${\mathrm{B}}_{84}$ as particularly stable planar clusters beyond the well-known ${\mathrm{B}}_{36}$, reproducing density-functional theory trends in formation energies. Independent validation using a machine learning force field–accelerated global structure search across both planar and three-dimensional manifolds confirms these predictions, while energy gaps, in this size range, remain small enough that planar forms stay competitive and are further stabilized on substrates. This resulting framework provides fundamental insights into boron chemistry and a practical route to rational design and scalable prediction of boron-based nanostructures.

We report a comprehensive experimental investigation of the magnetic ground state in ${\mathrm{ZnCoP}}_2{\mathrm{O}}_7$, where ${\mathrm{Co}}^{2+}$ ions in octahedral coordination realize an effective $J_{\mathrm{eff}}=1/2$ state and form a quasi-one-dimensional zigzag lattice comprising alternating edge-shared dimers. This unique magnetic geometry promotes strong frustration through competing nearest-neighbor and next-nearest-neighbor exchange interactions. Using complementary $\mathrm{dc}$ and $\mathrm{ac}$ magnetic susceptibility, specific heat, inelastic neutron scattering (INS), muon spin relaxation ($\mu \mathrm{SR}$) measurements, and ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR) experiments, we find no evidence of long-range magnetic order down to $\simeq 30\mathrm{mK}$, despite sizable antiferromagnetic interactions. Instead, persistent low-temperature spin dynamics, broad diffuse magnetic scattering, and the absence of sharp dispersive magnetic excitations reveal a highly correlated dynamic ground state. These observations identify ${\mathrm{ZnCoP}}_2{\mathrm{O}}_7$ as a rare example of a quasi-one-dimensional, spin-orbit-coupled quantum magnet exhibiting key experimental signatures consistent with a spin liquid ground state. The most likely microscopic origin of this spin liquid state is the combined effect of frustrated competing exchange interactions, low dimensionality, and spin-orbit entanglement.

The nature of superconductivity in $2H\text{−}{\mathrm{NbSe}}_2$ has generated sustained debate in the recent past. While angle resolved photoemission spectroscopy data have been interpreted as evidence for multiband superconductivity, the data from scanning tunneling microscope experiments relate to strongly anisotropic single-band superconductivity. In the later case, the charge density wave (CDW) order mimics the multigap character. Because the CDW reconstructs the Fermi surface and modifies the superconducting gap distribution, disentangling intrinsic multiband pairing from CDW-related effects is challenging. To address this issue, we investigate single-crystalline $2H$-NbSeS, a mixed-chalcogen analog of $2H\text{−}{\mathrm{NbSe}}_2$ in which random Se/S substitution suppresses long-range CDW order while preserving the layered crystal structure $P{6}_3/mmc$. The material becomes superconducting below $T_c\approx 6.0\mathrm{K}$ with moderate magnetic anisotropy $\gamma \approx 3.2$. The upper critical field $H_{c2}\left(T\right)$ exhibits a pronounced upward curvature that cannot be described within a single-band framework but is well captured by a dirty-limit two-band model with a large diffusivity ratio. This indicates strong band-dependent scattering. The in-plane upper critical field $H_{c2}^{\parallel ab}\left(0\right)\approx 14.7\mathrm{T}$ exceeds the weak-coupling Pauli limit. Measurements of the lower critical field, the superfluid density, and the electronic specific heat are consistent with an interpretation in terms of a fully gapped superconducting state with two nodeless gaps of different magnitudes.

Altermagnets host spin-split electronic bands despite zero net magnetization, opening new routes for spintronics beyond conventional ferromagnets. Going beyond symmetry-based classifications, which specify allowed terms but not their hierarchy, here we use first-principles calculations and Wannier Hamiltonian engineering to uncover the microscopic bonding contributions of altermagnetic spin splitting in the $g$-wave altermagnet ${\mathrm{Co}}_{1/4}{\mathrm{NbSe}}_2$. We show that the splitting is captured by a short-range tight-binding model, establishing its local origin. By selectively controlling hopping channels, we demonstrate that the dominant contribution arises not from direct magnetic-ion hopping, but from ligand-mediated hybridization that transfers anisotropy to itinerant states. This identifies ligand-assisted coupling as a dominant mechanism driving altermagnetic spin splitting in intercalated metals, providing a microscopic bridge between minimal models and material-specific electronic structure calculations in altermagnets.

In this work, we demonstrate traveling-wave-mediated remote magnon-magnon coupling over a distance exceeding 2 meters, extending the range of magnetic interactions to the meter scale. For long-range magnon-magnon coupling, the relatively small coupling strength makes propagation loss non-negligible, rendering conventional spectroscopy unreliable for characterizing the coupled-mode structure. To address this issue, we employ the determinant of the two-port scattering matrix, $det\widehat{S}$, as a qualitative spectral observable. Using this observable, we reproduce the widely reported characteristic evolution from coherent to dissipative coupling regimes under continuous phase tuning. This work extends the spatial range of magnetic interactions and advances the characterization of weak magnon-magnon coupling, providing a basis for developing multi-node magnonic networks.

We investigate two thermospintronic responses in proximity-induced superconductors with spin-orbit coupled band: the spin Nernst effect and the thermal Edelstein effect stemming, respectively, from momentum-space and mixed superconducting Berry curvatures. We unveil that the Bloch band spin-orbit coupling and pairing are entangled in shaping the superconducting Berry curvatures rather than in an additive manner. The resulting thermospintronic responses are significantly enhanced at low temperatures by the emergence of Bogoliubov-Fermi surface, and can be effectively controlled by tuning the latter. The effects render a probe of Bogoliubov-Fermi surface and superconducting Berry curvatures supported by it. Our work reveals Berry curvature properties in topologically trivial proximity superconductors with spin-orbit coupling, and opens a new route to superconducting spintronics.

Unconventional superconductivity is generally expected to be strongly suppressed by nonmagnetic disorder, as captured by Abrikosov-Gor'kov (AG) theory. However, several materials, including transition metal dichalcogenides (TMDs), exhibit signatures of unconventional pairing despite relatively high resistivities, suggesting a breakdown of the conventional relation between momentum relaxation and pair breaking. Here, we study this problem in H-phase TMDs by computing the disorder-dressed pairing susceptibility. We employ a minimal model with spin-orbit coupling and include an impurity potential that mimics a common lattice defect, namely, a chalcogen vacancy or site ad-atom. This yields to an extended impurity potential, which we compare with the commonly considered on-site (point defect) potential. We evaluate the momentum-relaxation rate and the pair-breaking rate on equal footing. We find that extended impurity potentials lead to a parametrically reduced pair-breaking rate compared with the transport scattering rate, with $\mathrm{\Gamma }{\tau }_D\sim 1/3$ over a wide parameter range. This reduction originates from the momentum structure of the disorder potential, which partially matches the internal structure of the superconducting gap and suppresses pair-breaking processes. As a result, unconventional pairing states are significantly more robust than predicted by standard AG theory. Our results provide a natural explanation for the persistence of unconventional superconductivity in systems with strong disorder and substantially alleviate the apparent conflict between high resistivity and unconventional pairing in materials such as $4Hb\text{−}{\mathrm{TaS}}_2$.

Superconductivity is usually assumed to arise from an attractive interaction. In this work we show that strong pairing is possible solely from kinetic energy even without a net attraction. We demonstrate a high-temperature kinetic superconductor in a simple lattice model with nearest-neighbor hopping ($t$) projected onto a constrained Hilbert space, analogous to the $t\text{−}J$ model with $J=0$, where kinetic magnetism has been previously studied. Using density matrix renormalization group (DMRG) on cylinders up to width $L_y=8$, we find a superconducting ground state exhibiting a key difference from high-$T_c$ cuprates: both the pairing gap and phase stiffness increase with doping ($x$). We find pairing gaps, determined from spin and single-electron charge gaps, exceeding $1.5t$. This model can be realized within the double Kondo lattice model, relevant to bilayer nickelates, in the limit of strong interlayer spin coupling ($J_{\perp }/t\to +\infty$) and a balancing interlayer repulsion ($V$). Importantly, the double Kondo model does not fundamentally restrict $J_{\perp }/t$, suggesting the potential for high critical temperatures ($T_c$) approaching $0.5t$. While this idealized limit predicts large pairing gaps, we show a smooth connection to the more realistic regime with $J_{\perp }\sim t$, albeit with a reduced pairing gap of approximately $0.1t$. Assuming $t\sim {10}^3\mathrm{K}$ in typical solid-state systems, our model suggests the exciting possibility of achieving $T_c$ of hundreds of Kelvin. We propose searching for bilayer materials with reduced out-of-plane lattice constants to better approximate the conditions of our ideal model.

We investigate the Mott-superfluid transition in a two-component Bose-Hubbard model with local Rabi coupling, focusing on the asymmetric regime where interaction, hopping, and chemical-potential imbalances compete with coherent interconversion. We show that the transition is governed by the softening of the lowest eigenmode of the full two-component response kernel rather than by the atomic gaps of either component separately. This eigenmode-based description clarifies the role of the symmetric common-mode channel and shows how local Rabi mixing reorganizes the Mott boundaries beyond the conventional two-component Bose-Hubbard scenario. Combining an analytical common-mode reduction with exact local susceptibility calculations and numerical determination of the phase boundary, we demonstrate that the first-lobe tip can evolve nonmonotonically with increasing Rabi coupling. Its minimum coincides with the maximum of the dominant susceptibility mode, signaling a crossover from softening to restiffening of the critical collective response. These results provide a susceptibility-based interpretation of Mott criticality in Rabi-coupled lattice bosons and identify clear signatures distinguishing the Rabi-coupled system from the conventional two-component Bose-Hubbard model.

The kagome compound ${\mathrm{CsTi}}_3{\mathrm{Bi}}_5$ serves as a natural counterpart to the extensively studied ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$, offering an ideal platform for directly comparing their emergent physical properties. Here, we employ ultrafast pump-probe spectroscopy to investigate the nonequilibrium carrier dynamics and collective excitations in ${\mathrm{CsTi}}_3{\mathrm{Bi}}_5$. The quasiparticle relaxation consists of several decay components, among which the fast subpicosecond decay is governed by the electron-phonon ($e\text{−}\text{ph}$) coupling. The extracted coupling constant of approximately $0.413\pm 0.007$ is smaller than that reported for ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. This weak-coupling strength may be one factor contributing to the absence of a charge-density-wave (CDW) order in ${\mathrm{CsTi}}_3{\mathrm{Bi}}_5$, even when its Van Hove singularities are tuned to the Fermi level, suggesting that $e\text{-ph}$ coupling may play an important role in stabilizing the CDW state in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. In addition, a coherent acoustic phonon mode with a frequency of 0.012 THz is identified, corresponding to a sound velocity of $v_s=1460$ m/s. Combined with the absence of any observed coherent optical phonon modes, the anomalous hardening of this mode with increasing temperature further supports weak $e\text{-ph}$ coupling. Together, these results advance the understanding of nonequilibrium carrier and lattice dynamics in kagome materials.

Ruddlesden-Popper (RP) nickelates superconduct when pressure suppresses intertwined charge- and spin-density waves. Here, we employ measurements of quantum corrections to magnetoconductivity as a probe of the dimensionality, phase coherence, and scattering mechanisms of the underlying single-crystal trilayer RP nickelate ${\mathrm{Pr}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ and ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$. We observe signatures of two-dimensional (2D) weak localization (WL), implying that the in-plane electron transport is in the quantum diffusive regime, while the out-of-plane transport is incoherent, and the electronic ground state is a quasi-2D disordered Fermi liquid. Application of pressure up to 3 GPa continuously suppresses signatures of WL, potentially signaling a 2D/3D dimensional crossover and an eventual pressure-driven transition into a superconductor.

We theoretically investigate acoustic spin resonance in a spatially homogeneous spinor polariton condensate. A longitudinal acoustic wave with a suitable in-plane anisotropic strain component generates a time-periodic strain-induced effective magnetic field acting on the condensate pseudospin. In contrast to the usual scalar acoustic modulation of the polariton energy, the anisotropic part of the strain response acts as an ac in-plane effective magnetic field in polarization space. When this field is transverse to the static in-plane linear-polarization splitting, it resonantly drives polarization oscillations. We show that spin-dependent interactions shift the resonance and produce nonlinear line shapes, while gain, reservoir dynamics, and spin relaxation make the response dissipative and history dependent, producing finite-rate amplitude-cycle hysteresis under the stated protocol. In the presence of lifetime anisotropy, the condensate can develop a bifurcated stationary state with finite circular polarization, and a frequency-selective acoustic protocol can reverse the circular polarization of a condensate prepared on one undriven branch and transfer it to an opposite-$S_z$ driven state. A Zeeman splitting provides an additional conservative knob for tuning the resonance frequency. Our results identify coherent acoustic driving as a route to resonant, nonlinear, and switchable control of polariton pseudospin dynamics.

In collinear altermagnets, the real-space rotational symmetry of opposite spin sublattices generates a large nonrelativistic spin-splitter current. Orbital transport in this setting has remained largely unexplored. Here, we introduce the orbital-splitter current (OSC), an orbital analog of the spin-splitter current, and derive its Drude and orbital Berry curvature contributions using a density-matrix framework. We show that the $d$-wave altermagnet ${\mathrm{FeSb}}_2$ realizes a purely intrinsic OSC because mirror symmetries suppress the Drude channel by forcing the orbital magnetic moment to vanish. The OSC response is strongly anisotropic, and for selected field orientations it can significantly exceed the spin-splitter current. Furthermore, using an effective altermagnet-ferromagnet model, we show that the OSC can generate a fieldlike torque, and the combined action of the orbital- and spin-splitter currents can reduce the magnetization switching time.

In contrast to the fractional quantum Hall (FQH) effect, where electron density fixes the applied magnetic field, fractional Chern insulators (FCIs) can realize FQH states in comparatively weak or even zero magnetic fields. Previous theoretical work highlighted magic-angle graphene as a promising FCI platform, satisfying the twin requirements of flat Chern $\pm 1$ bands and lowest-Landau-level-like quantum geometry. Indeed, recent experiments have demonstrated FCIs in magic angle graphene with weak magnetic fields. Here we conduct a detailed theoretical study of the most prominent FCI state observed, and we clarify the role of the magnetic field in stabilizing this state. We introduce two new technical tools: first, we generalize the notion of ideal quantum geometry to Hofstadter minibands, and second, we extend the Hartree-Fock theory of magic-angle graphene to finite field, to account for the interaction-generated bandwidth. We show that magnetic field both dramatically reduces the effective bandwidth and improves the quantum geometry for hosting FCIs. Using density matrix renormalization group simulations of a microscopic model of magic-angle graphene, we establish the regime of bandwidth and quantum geometry indicators where FCIs are stabilized. Further characterizing the finite-field bands by the same quantities, we show how a zero-field charge density wave state gives way to an FCI state at a magnetic flux consistent with experiment. We also speculate on the other FCIs seen in the same experiments, including anomalous incompressible states and even-denominator fractions, which may host non-Abelian states. Finally, we propose a range of experimental parameters where FCIs should appear at zero magnetic field, when bandwidth is the limiting factor.

The layer Hall effect provides a prototypical example of a hidden layer response in van der Waals bilayers: opposite layers carry compensating Hall currents at zero out-of-plane electric field, while an applied out-of-plane electric field $E_z$ selects one layer over the other and switches the net Hall response. Here we show that this field-switching mechanism is not restricted to Hall transport, but follows from a general symmetry principle for response tensors. We formulate a selection rule for the layer-tensor effect (LTE) using Jahn symbols. For a tensor with Jahn symbol $J$ and rank $r$, the stacking operation that exchanges the two layers acts as a coset representative relating the $+E_z$ and $-E_z$ states. Tensor components that are odd under this operation are forced to cancel between layers at $E_z=0$, and acquire a macroscopic response satisfying $T_{\alpha }(+E_z)=-T_{\alpha }(-E_z)$. This criterion allows us to enumerate the symmetry-allowed electrically reversible tensor components associated with different Jahn symbols and to identify their physical realizations in common response tensors. We apply the theory to representative anomalous Hall, shift-current, nonlinear Drude, piezoelectric, spin Hall, and spin-photocurrent channels. Model calculations and first-principles simulations further confirm the predicted field-odd responses. Our results establish an electrically switchable LTE framework, providing a unified route to multifunctional layertronic responses in bilayer materials.

The chiral vortical effect (CVE)—an axial current driven by rotation in chiral matter—appears in systems ranging from relativistic fluids to Weyl semimetals. We present a quantum treatment of a rotating Weyl fermion in a finite cylinder that reproduces the on-axis current density obtained by Vilenkin in an infinite system, while revealing two additional phenomena. First, we find that the cross-sectional averaged current density vanishes in the thermodynamic limit, establishing that the bulk vortical response is purely a magnetization current. Second, for spin-polarized boundary conditions, we uncover a robust family of chiral modes that transport axial charge, $\mathrm{\Delta }Q=\chi N^2\mathrm{\Delta }\theta /4\pi$, under rotation by angle $\mathrm{\Delta }\theta$, where $\chi$ is the Weyl node chirality and $N$ is the number of chiral modes. The pump is independent of temperature, Fermi level, and Weyl velocities, but depends on the UV-sensitive number $N$. These results clarify the quantum structure of the bulk CVE and reveal a boundary-enforced chiral spectral structure underlying vortical response in Weyl systems.

We give an exact form of the density matrix for the spin-1/2 Kitaev spin liquid, expressed in terms of spin operators, and study the entanglement structure of the Kitaev honeycomb model within the spin framework. We show that the density matrix is naturally organized by equivalence classes of string operators associated with the underlying gauge structure of the model. With the explicit form of the density matrix, plus the exact Gauss law of the emergent gauge theory and the exact 1-form Wilson symmetry in the Kitaev model, we demonstrate the existence of the underlying symmetry-resolved block-diagonal structure of the reduced density matrix, which gives rise to the extensive degeneracy in the entanglement spectrum. The block-diagonal structure is then proven to be responsible for the separability of the entanglement entropy into the gauge and matter parts. Furthermore, we extend the formalism to subsystems with an odd number of lattice sites, revealing a relation between the entanglement spectrum and the fermion parity that is seldom mentioned in the literature.

Quantum spin Hall transport in InAs/GaInSb-based two-dimensional topological insulators can be limited by parasitic bulk and edge contributions. We demonstrate that these limitations are effectively mitigated through electrostatic control in dual-gated InAs/GaInSb/InAs trilayer quantum wells grown on AlSb quasisubstrates. In macroscopic Hall bars exceeding the phase coherence length, a multiprobe analysis reveals an insulating bulk and a constant edge resistance over a wide electric-field range. In microscopic devices with edge lengths below the phase coherence lengths, the edge resistance remains robust and quantized across a broad field range, revealing the intrinsic resilience of helical edge channels to electric-field perturbations. Only beyond a threshold value, parasitic edge contributions emerge. These results establish dual gating as a reliable strategy to suppress parasitic conduction while stabilizing helical edge transport, providing a versatile and reproducible platform for tunable topological transport in III–V quantum spin Hall systems.