Multilayer graphene materials have recently emerged as a fascinating versatile platform for correlated electron phenomena, hosting superconductivity, fractional quantum Hall states, and correlated insulating phases. A particularly striking experimental observation is the recurring correlation between nematicity in the normal state—manifested by spontaneous breaking of the underlying $C_3$ symmetry—and the stabilization of robust superconducting phases. Despite its ubiquity across different materials, devices and experiments, this trend has thus far lacked a clear microscopic explanation. In this work, we identify a concrete mechanism linking nematic order to enhanced superconductivity. We demonstrate that $C_3$-symmetry breaking strongly reshapes the Bloch wave functions near the Fermi level, producing a pronounced enhancement and redistribution of the so-called quantum metric. This effect drastically amplifies superconducting pairing mediated by the quantum geometric Kohn-Luttinger mechanism [G. Shavit et al., Phys. Rev. Lett. 134, 176001 (2025)]. Our analysis reveals that nematicity naturally boosts the superconducting coupling constant in experimentally relevant density regimes, providing a compelling explanation for observed correlations. These results establish the central role of geometric effects in graphene superconductivity and highlight nematicity as a promising avenue for engineering stronger unconventional superconducting states.

We report a ferromagnetic-like anomalous Hall resistivity and giant isotropic negative magnetoresistance (NMR) in the antiferromagnetic half-Heusler compound DyPdBi. The FM-like anomalous Hall resistivity appears exclusively in antiferromagnetic state II, yet it is not coupled to magnetization, indicating a Berry-curvature origin. Additionally, the magnetoresistance drops by 98%, and the NMR persists above the Néel temperature ($T_{\mathrm{N}}$). We attribute both phenomena to a half-topological-semimetal (HTS) state, similar to that proposed for TbPdBi, arising from weak band inversion strength (BIS). This state enhances spin polarization, reducing Berry curvature cancellation and strengthening anomalous Hall effect (AHE). These observations suggest that weak BIS in the RPdBi family gives rise to an HTS that potentially interacts with exotic spin states, producing an exceptionally large AHE. This study highlights a strategy for engineering large AHE in half-Heusler antiferromagnets, and advances the further topological spintronics design.

Anisotropic skyrmion Hall effect (A-SkHE) in two-dimensional (2D) magnetic systems represents a captivating phenomenon in condensed-matter physics and materials science. While conventional antiferromagnetic systems inherently suppress this effect through parity-time symmetry-mediated cancellation of Magnus forces acting on skyrmions, A-SkHE is primarily confined to ferromagnetic platforms. Here, we present a paradigm-shifting demonstration of this phenomenon in spin-splitting 2D antiferromagnets through the investigation of altermagnetic skyrmions. Combining comprehensive symmetry analysis with theoretical modeling, we elucidate the mechanism governing A-SkHE realization in 2D altermagnetic systems and establish a quantitative relationship between the transverse velocity of altermagnetic skyrmions and applied current orientation. Using first-principles calculations and micromagnetic simulations, this mechanism is further illustrated in a prototypical altermagnetic monolayer ${\mathrm{V}}_2\mathrm{SeTeO}$. Crucially, we identify that the $\left[C_2\parallel C_{4z}\mathbf{t}\right]$ symmetry-protected anisotropic field serves as the critical stabilizer for maintaining the A-SkHE in this system. Our results greatly enrich the research on 2D altermagnetism and skyrmions.

This paper presents a theoretical investigation of electron-magnon scattering processes in the ultrafast demagnetization in itinerant ferromagnets. In the framework of a ferromagnetic model system, we compute the spin-dependent dynamics of electrons in itinerant Bloch states by including electron-magnon and electron-electron scattering processes on an equal footing. While the former process flips the electronic spin accompanied by the creation or destruction of a magnon, the latter exchanges electronic angular momentum with the lattice due to the influence of spin-orbit coupling. We show that, for a realistic choice of the electron-magnon interaction and deposited pulse energy, the interplay of these two different scattering mechanisms leads to the creation of magnons and a transfer of angular momentum to the lattice that constitutes an essentially nonequilibrium microscopic scenario for the ultrafast demagnetization process in itinerant ferromagnets.

Can strong repulsive interactions be shown to give rise to pairing in a controlled way? We find that for a single flavor-polarized band, there is a small expansion parameter in the low density limit, once the Bloch wave-function form factor is taken into account. A perturbative expansion is possible, even if the interaction is much stronger than the Fermi energy ${\epsilon }_F$. As a matter of principle, our work shows analytically how strong pairing can emerge from strong repulsion. We illustrate our method with two examples: a two-dimensional Dirac model and a one-dimensional tight-binding model with two orbitals. In the latter case, using density matrix renormalization group, we show that the analytical theory indeed guided us to discover the parameter regime where $p$-wave pairing with order-1 strength is dominant.

We report the emergence of Majorana flat bands (MFBs) in the vortex line of superconducting (SC) time-reversal symmetry-breaking Weyl semimetals. By considering a Weyl semimetal as a stack of Chern insulators with varying Chern numbers along one ($z$) direction, we decompose the vortex bound states of SC Weyl semimetals into those of $k_z$-resolved SC Chern insulators. Through analytical and numerical calculations of the topological phase diagram of the SC Chern insulators, we explain the appearance of MFBs and determine the exact boundaries of them. Notably, the tuning of chemical potential or pairing strength results in the MFBs along the entire $k_z$ axis. We find that the MFBs are absent in SC type-$\mathrm{II}$ Weyl semimetals due to the inversion symmetry-breaking term. To characterize the MFBs, we propose a $k_z$-resolved $Z_2$ Chern-Simons invariant as the topological indicator. Finally, we take an attractive Hubbard interaction into consideration, and the aforementioned SC Weyl semimetal with BCS pairing can be realized under appropriate parameters.

Classical and quantum Markov networks—including Gibbs states of commuting local Hamiltonians—are characterized by the vanishing of conditional mutual information (CMI) between spatially separated subsystems. Adding local dissipation to a Markov network turns it into a hidden Markov network, in which CMI is not guaranteed to vanish even at long distances. Nevertheless, it is unclear whether the Markov property still holds approximately after dissipation, i.e., whether CMI decays with distance. In this work, we show that high-temperature hidden Markov networks are approximately Markovian under a wide class of local perturbations. We establish that CMI in high-temperature Gibbs states subject to local dissipation decays exponentially: (i) for classical Hamiltonians subject to arbitrary local transition matrices and (ii) for commuting local Hamiltonians subject to unital channels that obey certain mild restrictions. Our result provides the first rigorous understanding of long-range CMI in a broad class of models, offering a new lens to analyze quantum states through their information structure. It also leads to new results in understanding teleportation, mixed-state phases of matter, state preparation, and compressibility of quantum states.

We investigate low-energy excitons in rhombohedral pentalayer graphene encapsulated by hexagonal boron nitride (hBN/R5G/hBN), focusing on the regime at the experimental twist angle $\theta =0.{77}^{\circ }$ and with an applied electric field. We introduce a new low-energy two-band model of rhombohedral graphene that captures the band structure more accurately than previous models while keeping the number of parameters low. Using this model, we show that the centres of the exciton Wannier functions are displaced from the moiré unit cell origin by a quantized amount—they are instead localized at $C_3$-symmetric points on the boundary. We also find that the exciton shift is electrically tunable: by varying the electric field strength, the exciton Wannier center can be exchanged between inequivalent corners of the moiré unit cell. Our results suggest the possibility of detecting excitonic corner or edge modes, as well as novel excitonic crystal defect responses in hBN/R5G/hBN. Lastly, we find that the excitons in hBN/R5G/hBN inherit excitonic Berry curvature from the underlying electronic bands, enriching their semiclassical transport properties. Our results position rhombohedral graphene as a compelling tunable platform for probing exciton topology in moiré materials.

While type-II silicon clathrates have shown promising room-temperature photoluminescence, their intrinsic optical properties remain unclear due to the presence of surface oxides, inhomogeneous and significant residual sodium concentrations, and contributions from disordered phases. These factors have hindered reliable identification of the emission band and limited development of the clathrates as light-emitting materials. In this work, we present a systematic photoluminescence (PL) study of deuterium-passivated, low-Na-doped, Si clathrate films, in which Na-related donor states and native defect levels are significantly reduced. A previously unrecognized emission feature associated with a surface oxide layer is identified and chemically removed, revealing a sharper emission spectrum composed of two dominant emission bands. We associate the higher energy band with the emission from the clathrate framework and the lower one with hydrogenated disordered or amorphous Si present as an impurity phase in the material. Temperature- and excitation-dependent PL measurements place the optical band gap of the clathrate phase near 1.9 eV, consistent with theoretical predictions. These results resolve long-standing ambiguities in Si clathrate PL emission and demonstrate a practical route to accessing near-intrinsic optical transitions. This lays the groundwork for engineering clathrate-based optoelectronic materials and highlights their potential as silicon-compatible light emitters.

Photovoltaic Hall effect, i.e., generation of a photocurrent perpendicular to the bias electric field, is an interesting platform of Berry curvature engineering by external fields. Floquet engineering aims at generation of light-induced Berry curvature associated with topological phase transition in solids, which may manifest itself as a light-induced anomalous Hall effect. However, recent studies have pointed out a larger contribution by momentum asymmetry of photocarriers, termed a field-induced circular photogalvanic effect. Except for numerical studies, the two mechanisms have been described by different theoretical frameworks, hindering a coherent understanding. Here, we develop a unified theory of the photovoltaic Hall effect capable of describing both mechanisms on an equal footing. We reveal that the bias electric field alters the interband transition dipole moment and transition energy, both contributing to the field-induced circular photogalvanic effect in nonmagnetic materials. These effects are governed by an electric field-induced Berry curvature and the shift vector coupled to bias field, respectively. A resonant enhancement of the transverse photocurrent is found in GaAs owing to the topological character of the valence band. We also clearly distinguish the anomalous Hall effect by light-dressed states within the density matrix calculation using the length gauge. Our theory unifies a number of nonlinear optical processes in a physically transparent way and presents a geometric picture of the third-order nonlinear response under light and bias fields, shedding new light on Berry curvature engineering.

Monolayer 1$T{}^{\prime }-{\mathrm{MoS}}_2$ exhibits spin- and valley-dependent massive tilted Dirac cones with two velocity correction terms in low-energy effective Hamiltonian. We theoretically investigate the longitudinal diffusive magneto-conductivity of monolayer 1$T{}^{\prime }-{\mathrm{MoS}}_2$ by using the linear response theory. It is shown that the Weiss oscillations are polarized in spin and valley degrees of freedom, under uniform electric fields and a weak one-dimensional spatially periodic electrostatic potential modulation. The spin polarization, the valley polarization and the spin-valley polarization can be switched by flipping the external electric fields. The polarization is found not only in the amplitudes but also in the periods of the Weiss oscillations. It is found that the period polarization in Weiss oscillations originates from the polarized effective Fermi energies or the polarized Landau level spacing scales. In Weiss oscillations, polarization in amplitude does not imply the presence of polarization in period, whereas polarization in period is accompanied by polarization in amplitude. The superposition of polarization in amplitude and polarization in period enables the appearance of considerable polarization in Weiss oscillations under relatively weak external electric fields.

Deciphering the atomistic mechanism governing humidity-dependent interfacial friction remains a fundamental challenge across physics, chemistry, medicine, and materials science. Here, we employ first-principles calculations to systematically investigate the frictional behaviors of bilayer graphene (BLG) with varying interfacial water (${\text{H}}_2\text{O}$) coverage, with a particular focus on the contrasting responses of commensurate and incommensurate contacts. Our findings reveal a striking dichotomy: As ${\text{H}}_2\text{O}$ coverage increases to approximately 0.4 monolayer, commensurate BLG interfaces experience a dramatic reduction in friction, reaching a minimum, whereas incommensurate contacts exhibit a moderate increase in friction, peaking near 0.6 monolayer. Beyond these critical humidity cites, friction in commensurate systems gradually increases toward a saturation regime, while incommensurate systems display a declining trend before plateauing. To validate these distinct behaviors, we establish a generalized registry index framework that extends the conventional registry index [N. Marom $et al$., Phys. Rev. Lett. 105, 046801 (2010)] by explicitly incorporating (i) interlayer-distance-dependent vdW interactions modulated by water intercalation, (ii) humidity-induced commensurate-incommensurate phase transitions, and (iii) molecular pinning sites imparted by confined ${\text{H}}_2\text{O}$ molecules within the BLG heterostructure. Collectively, this work not only reveals the atomistic mechanism of humidity as an effective tuning parameter for frictional control in two-dimensional materials but also provides a robust descriptor with predictive power for the rational design of adaptive, environment-responsive nanolubrication systems.

We consider an electron interacting locally with two-level systems (TLSs) as an archetypal model for charge transport in the presence of inelastic scatterers. To assess the importance of quantum effects in the optical and dc conductivity we solve the model numerically using the finite temperature Lanczos method, and compare the results with both dynamical mean-field theory and the relaxation time approximation. In the slow fluctuation limit, the coupling to the TLSs causes transient localization of the carriers analogous to the one found in the electron-boson scattering problem, featuring enhanced resistivities and displaced Drude peaks. Fast inelastic scatterers suppress localization, restoring a more conventional regime where transport and optical properties are governed by independent scattering events.

We present an infrared spectroscopy study of the layered topological semimetal ${\mathrm{TaNiTe}}_5$, a material with a quasi-one-dimensional structure and strong in-plane anisotropy. Despite its structural features, infrared reflectivity and electronic transport measurements along the $a$ and $c$ crystallographic axes show metallic behavior without evidence of reduced dimensionality. Optical conductivity reveals an anisotropic but conventional metallic response with low scattering rates and a single sharp infrared-active phonon mode at $396{\mathrm{cm}}^{-1}\left(49\mathrm{meV}\right)$. Ab initio calculations closely match the experimental optical data and confirm a three-dimensional electronic structure. Our results demonstrate that ${\mathrm{TaNiTe}}_5$ behaves as a three-dimensional anisotropic semimetal in its electronic and optical properties.

We study the dynamic response of magnetic domain walls in low-lying excited states of an Ising chain to an oscillating transverse field. Based on the exact instantaneous eigenstates, we find that when the frequency of the external field is in off-resonant regions, the domain wall exhibits Bloch oscillation, maintaining the magnetic order. However, the magnetic order is destroyed when the field is at resonant frequency. Numerical simulations of the dynamics of magnetization and entanglement entropy for initial states with single and double domain walls accord with the predictions. These findings reveal the nontrivial effect of a monochromatic electromagnetic field on quantum spin dynamics.

We report anomalously large shot noise in metallic and tunnel nanojunctions of $\beta$-tantalum, a metal characterized by a small negative temperature coefficient of resistivity inconsistent with both the Fermi liquid theory of Bloch electrons and single-particle localization. Fano factors are enhanced, and cluster around even multiples of the values expected for Fermi liquids, suggesting the possibility of pairwise electron correlations akin to local groups of Cooper pairs. The importance of spin for this state is suggested by the effects of magnetic impurities. Additional evidence for correlations is provided by the reduced density of states near the Fermi level revealed by point contact spectroscopy and first principles calculations. Our findings indicate that electron correlations may play an important role in a much larger class of materials than previously believed.