In this Letter, we investigate the dissipative dynamics at the edge of Laughlin fractional quantum Hall (FQH) states starting from the hydrodynamic framework of the composite boson theory recently developed by G. M. Monteiro et al. [Phys. Rev. B 109, 174525 (2024)]. Critical to this description is the choice of boundary conditions, which ultimately stems from the choice of hydrodynamic variables in condensate degrees of freedom. Given the gapped nature of bulk, one would expect dissipation effects to play an important role only near the FQH edge. Thus, one envisions a scenario where the bulk hydrodynamic equations remain unmodified, while the dissipation effects are introduced at the edge via boundary conditions. We have recently shown that the anomaly requirements fix the boundary conditions of the FQH fluid to be no-penetration and no-stress boundary conditions. In this work, we introduce energy dissipation in the no-stress boundary condition leading to charge diffusion at the boundary. The resulting dissipative edge dynamics is quite rigid from a hydrodynamic perspective, as it has to preserve the edge charge continuity and the anomaly structure. We show that the diffusive edge dynamics with fluctuation-dissipation relations within a power counting scheme belong to the Kardar-Parisi-Zhang universality class.

Photoinduced effects are now reckoned to be important tools to reveal a rich gamut of entrancing physics in topological materials, which are normally inaccessible to conventional probes. Here we investigate one of these intriguing effects, namely, optical pseudospin injection (OPI) beyond ordinary Weyl semimetals (WSMs), specifically in multi-WSMs (mWSMs) and higher-order WSMs. Remarkably, we demonstrate that OPI in mWSMs is independent of the frequency of the light and linearly proportional to the quantized topological charge as a consequence of the inherent band linearity in their dispersions. Interestingly, while the response does not depend on the tilting of a type-I node, it is a decreasing function of the same in type-II mWSMs. We also reveal that the frequency independence can be destroyed either by going beyond a certain cutoff frequency under lattice regularization or by going to a higher-order Weyl phase. The predicted signatures of OPI beyond the ordinary WSM could be experimentally exploited, leading to effective access as well as distinguishing between different nontrivial Weyl topologies.

Two-dimensional van der Waals materials offer a highly tunable platform for generating emergent quantum phenomena through symmetry breaking. Stacking-induced symmetry breaking at interfaces provides an effective method to modulate their electronic properties for functional devices. Here, we strategically stack bilayer graphene with black phosphorus, a low-symmetry semiconductor, to break the symmetries and induce the nonlinear Hall effect (NLHE) that can persist up to room temperature. Intriguingly, it is found the NLHE undergoes sign reversals by varying the electrical displacement field under fixed carrier density. The scaling analysis reveals that the sign reversal of the NLHE is contributed from both the Berry curvature dipole (BCD) and extrinsic scatterings. The displacement field-induced sign reversal of the BCD indicates asymmetric distributions of Berry curvature hot spots across different Fermi pockets in bilayer graphene. Our findings suggest that symmetry engineering of van der Waals heterostructures is promising for room-temperature applications based on nonlinear quantum devices, such as high-frequency rectifiers and wireless charging.

The optical manipulation of magnon states in antiferromagnets (AFMs) holds significant potential for advancing AFM-based computing devices. In particular, two-magnon Raman scattering processes are known to generate entangled magnon pairs with opposite momenta. We propose to harness the dynamical backaction of a driven optical cavity coupled to these processes, to obtain steady states of squeezed magnon pairs, represented by squeezed Perelomov coherent states. The system's dynamics can be controlled by the strength and detuning of the optical drive and by the cavity losses. In the limit of a fast (or lossy) cavity, we obtain an effective equation of motion in the Perelomov representation, in terms of a light-induced frequency shift and a collective induced dissipation which sign can be controlled by the detuning of the drive. In the red-detuned regime, a critical power threshold defines a region where magnon-pair operators exhibit squeezing, a resource for quantum information, marked by distinct attractor points. Beyond this threshold, the system evolves to limit cycles of magnon pairs. In contrast, for resonant and blue detuning regimes, the magnon-pair dynamics exhibits limit cycles and chaotic phases, respectively, for low and high pump powers. Observing strongly squeezed states, auto-oscillating limit cycles, and chaos in this platform presents promising opportunities for future quantum information processing, communication developments, and materials studies.

There is evidence for competition between superconductivity and short-range charge-density wave order in a number of cuprate compounds and especially in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6+x}$. Here, we use a nonlinear sigma model of such competition to study the effects of spatially correlated disorder in the chain layers and delta-correlated disorder in the ${\mathrm{CuO}}_2$ layers. The first is relevant to the oxygen ortho structure and the latter may be induced by electron irradiation. We find that reducing the correlation length of the potential on the chain layers decreases the size of the charge-density wave structure factor but has little effect on its temperature dependence, as observed experimentally. At the same time, the charge-density-wave correlation length decreases more than is seen in the experiment. The temperature at which the structure factor peaks coincides with $T_c$ and both decrease when disorder is introduced into the ${\mathrm{CuO}}_2$ planes. Strengthening this disorder reduces the magnitude of the structure factor and eventually turns it into a monotonic function of the temperature. This occurs despite an increase in the local magnitude of the charge-density wave order.

Inspired by recent predictions of superconductivity in B-C framework clathrates, we employ density functional theory to explore potential superconductors among hexagonal hydride-substituted compounds with compositions $X{\mathrm{B}}_8\mathrm{C}, X{\mathrm{B}}_7{\mathrm{C}}_2, X{\mathrm{B}}_6{\mathrm{C}}_3, X{\mathrm{B}}_3{\mathrm{C}}_6, X{\mathrm{B}}_2{\mathrm{C}}_7$, and $X{\mathrm{BC}}_8$. Our high-throughput calculations on 96 compounds reveal several dynamically stable candidates exhibiting superconductivity at ambient pressure. An analysis of the electronic structures and electron-phonon coupling demonstrates that ${\mathrm{CaB}}_8\mathrm{C}, {\mathrm{SrB}}_8\mathrm{C}$, and ${\mathrm{BaB}}_8\mathrm{C}$ possess superconducting transition temperatures ($T_c$) exceeding 50 K, with ${\mathrm{CaB}}_8\mathrm{C}$ exhibiting the highest predicted $T_c$ of 77.1 K among all stable compounds studied. These findings expand the family of B-C clathrate superconductors and provide valuable insights for experimental efforts aimed at discovering different superconducting materials.

Amorphous silicon nitride is a common material in microelectronics devices, which acts as an insulating barrier. Extended annealing times at elevated temperature can initiate crystallization of $\alpha \text{−}{\mathrm{Si}}_3{\mathrm{N}}_4$, which does not possess the same barrier properties. Molecular dynamics can resolve the fundamental mechanism for $\alpha \text{−}{\mathrm{Si}}_3{\mathrm{N}}_4$ crystallization and the influence of local environments. We compare two interatomic potentials and conclude that these models predict structural features (e.g., angular distributions and densities) which span the range of experimental measurements. We confirmed these models reproduce experimental estimates of activation energy and leveraged these models to identify crystallization drivers. We conclude that near-$T_g$, facet-dependent silicon nitride crystal growth rates can be predicted directly by either bulk or interfacial diffusion properties.

Nonlinear phononics in the terahertz fields offers transformative potential for novel optoferroic devices by enabling precise control over ferroelectric polarization in ferroelectrics via anharmonic phonon couplings. The atomic-scale response of ferroelectrics to terahertz fields is closely linked to the dynamics of multimode nonlinear interactions, and real-time structural and polarization evolution. However, capturing these dynamics experimentally and theoretically remains a challenge. Herein, we propose a molecular-dynamics-based approach, incorporating machine learning interatomic potentials, to realize accurate simulations of the real-time polarization switching behavior of ferroelectric ${\mathrm{KNbO}}_3$, capturing the full anharmonicity. We highlight the capabilities of the deep potential in predicting anharmonic features of density functional theory. We report that the ferroelectric mode, driven by the $A_1$ mode (at ∼17.56 THz) through the quadratic-linear coupling, initiates a fully switched state within 1 ps. Our observation enables an alternative route to investigating ultrafast polarization dynamics for terahertz excitation and may advance energy-efficient optoferroic applications.

We research the ground state of the $S=1$ XXZ spin chain with single-ion anisotropy, focusing on XY1, XY2 (spin nematic), Néel, and Haldane phases. Recently, it was reported that the four phases did not intersect at a single point using conventional numerical methods, which is inconsistent with the bosonization theory. In order to resolve this discrepancy, we propose a unified method to determine phase boundaries by combining conformal field theory with numerical diagonalization. In addition, we discuss the symmetry and universality class of the multicritical point.

The polar magnets $A_2{\mathrm{Mo}}_3{\mathrm{O}}_8$ ($A=\mathrm{Fe}$, Mn, Co, and Ni) feature a bipartite structure, where the magnetic $A^{2+}$ ions occupy two different sites with octahedral and tetrahedral oxygen coordinations. This bipartite structure provides a platform for the emergence of nontrivial magnetoelectric effects and intriguing excitation behaviors, and thus creates significant research interest. In this study, we conduct inelastic neutron scattering measurements on single crystals of ${\mathrm{Mn}}_2{\mathrm{Mo}}_3{\mathrm{O}}_8$, an L-type ferrimagnet in the $A_2{\mathrm{Mo}}_3{\mathrm{O}}_8$ family, to investigate its spin dynamics. The obtained magnetic excitation spectra reveal two distinct magnon dispersions corresponding to the octahedral and tetrahedral spins in ${\mathrm{Mn}}_2{\mathrm{Mo}}_3{\mathrm{O}}_8$. These magnon bands can be well described by a spin Hamiltonian including Heisenberg and single-ion anisotropy terms. Employing our effective spin model, we successfully reproduce the unusual temperature dependence of the L-type ferrimagnetic susceptibility through self-consistent mean-field theory. This research reveals the significance of the bipartite structure in determining the excitation properties of the polar magnets $A{}_2{\mathrm{Mo}}_3{\mathrm{O}}_8$ and provides valuable insights into the spin dynamics of L-type ferrimagnets.

Rare-earth–transition-metal ferrimagnetic alloys are known to show various unique features, especially near their magnetization compensation point. We report the sign reversal of unidirectional spin Hall magnetoresistance (USMR) in $\mathrm{W}/\mathrm{C}{{\mathrm{o}}_{100}}_{-x}\mathrm{G}{\mathrm{d}}_x$ systems across the magnetization compensation point, which is confirmed by varying the Gd concentration and temperature. We reveal that the sign of USMR is determined by the magnetization direction of the Co sublattice because the Gd sublattice plays negligible role in the spin-dependent scattering. Furthermore, in the vicinity of the compensation point, an enhancement of USMR at high magnetic field is observed, which differs markedly from conventional nonmagnetic metal/ferromagnetic metal systems. This peculiar field dependence stems from the spin-flop transition, which is unique to antiferromagnetically coupled materials. Our study highlights the potential of ferrimagnetic alloys to achieve high tunability of USMR.

We study the XXZ square lattice bilayer model with antiferromagnetic nonfrustrating long-range interactions that decay as a power law with the distance. Employing large-scale high-order series expansions with classical Monte Carlo integration $(\mathrm{pCUT}+\mathrm{MC})$ about the limit of isolated Heisenberg dimers in the rung-singlet phase, we investigate the one-triplon dispersion and the corresponding spectral weight along the parameter axes of the long-range decay exponent and the XXZ anisotropy. By tuning the latter, we observe two extended regions of 3D XY and Ising universality as well as 3D Heisenberg critical exponents at the isotropic point. Along the decay exponent axis, we demonstrate mean-field behavior for strong long-range couplings, the aforementioned three universality classes for sufficiently weak interactions, and continuously varying critical exponents in between. Using extrapolations, we are able to determine the one-triplon dispersion in a quantitative fashion up to the quantum-critical breakdown of the rung-singlet phase. This allows us to extract the dynamical critical exponent $z$ as a function of the decay exponent, displaying a universal behavior. The detected $z<1$ for small decay exponents is in agreement with the expected properties of the anomalous Goldstone modes in the ordered phases with broken continuous symmetry.

We present an in-depth analysis of MnRuAs, a compound crystallizing in the $P\overline{6}2m$ symmetry with a distorted kagome lattice, revealing its distinctive structural, magnetic, and electronic properties through state-of-the-art ab initio calculations. By incorporating correlation effects using the $\mathrm{DFT}+\mathrm{U}$ approach, we demonstrate the stabilization of MnRuAs, transforming its inherent dynamical instability into a robust ferromagnetic state with significant coupling along the $c$ axis. The calculated magnon dispersion reveals a parabolic profile with a minimum at the $\mathrm{\Gamma }$ point, indicative of ferromagnetic behavior. Furthermore, MnRuAs exhibits intriguing electronic properties, including a quasi-one-dimensional Fermi surface and the formation of a nodal sphere. Our study also delves into the electronic surface states and constant energy contours, offering valuable insights into the complex physics of this material.

We develop a quantitative theory of phonon magnetic moment in doped Dirac semimetals. Our theory is based on an emergent gauge field approach to the electron-phonon coupling, applicable to gapless systems. We find that the magnetic moment is directly proportional to the electrical Hall conductivity through the phonon Hall viscosity. Our theory is combined with the first-principles calculations, allowing us to quantitatively implement it to realistic materials. Magnetic moments are found to be of the order of a Bohr magneton for Raman-active phonon modes in graphene and ${\text{Cd}}_3{\text{As}}_2$. Our results provide practical guidance for the dynamical generation of large magnetization in quantum materials.

Flat bands induced by destructive interference of hoppings in frustrated lattices such as kagome metals, have been extensively studied in recent years. However, such flat bands usually appear in small portions of the Brillouin zone and are away from the Fermi level in the noninteracting limit (dubbed as “incipient”). Whether such incipient flat-band portions can induce very strong electron correlations is an open question. Recently, such incipient flat bands are found in frustrated kagome ${\mathrm{CsCr}}_3{\mathrm{Sb}}_5$ and triangular ${\mathrm{CrB}}_2$, which show moderately heavy-fermion behaviors and unconventional superconductivity. Here, by density functional theory plus dynamical mean-field theory calculations, we show that both compounds are typical Hund's metals. The incipient flat-band portions induce dips in hybridization functions, which further enhance the Kondo-like effect of Hund's metal, resulting in moderately heavy-fermion behaviors. This explains the origin of the heavy-fermion behaviors and pave the way for understanding the unconventional superconductivity in ${\mathrm{CsCr}}_3{\mathrm{Sb}}_5$ and ${\mathrm{CrB}}_2$. Our work demonstrates a flexible route for generating $d$-electron heavy fermions and for inducing unconventional superconductivity based on frustrated Hund's metals with portions of incipient flat bands. A large family of materials with kagome, triangular, and pyrochlore lattices consisting of Cr ($d^4$), Ru ($d^4$), and Fe ($d^6$) ions are promising candidates.