We study the orbital magnetic susceptibility of tilted massless Dirac fermions in two dimensions. It is well known that the type I massless Dirac fermions exhibit divergingly large diamagnetic susceptibility, whereas less is known about the type II and III cases. We first clarify that the orbital magnetic susceptibility is vanishing for types II and III in the continuum model. We then compare the three types of Dirac fermions for the lattice models. We employ three tight-binding models with different numbers of Dirac points, all of which are two-band models defined on a square lattice. For all three models, we find that the type I Dirac fermions show the divergingly large orbital diamagnetic susceptibility, whereas the type II Dirac fermions exhibit nondiverging paramagnetic susceptibility. The type III Dirac fermions exhibit diamagnetism but its susceptibility is small compared with the type I case.

III-Sb semiconductor nanostructures provide sophisticated materials for developing optoelectronic applications in the near- and midinfrared wavelengths, for which the capability of engineering band alignments and wave functions is highly desirable. Segregation and diffusion at the interfaces, however, are features commonly found in Sb-based structures, impacting device performance and optical properties. By using type-II ${\mathrm{GaAs}}_{1-\mathit{x}}{\mathrm{Sb}}_{\mathit{x}}/\mathrm{GaAs}$ quantum wells as a platform, we demonstrate the effects of short- and long-range disorders in their optical emission, resulting in localization effects, broadening, and the emergence of a lower-energy band. The luminescence is characterized by varying excitation power, temperature, and magnetic field. Our findings demonstrate the presence of local potential minima of $\sim 10\mathrm{meV}$ arising from the short-range contribution, the transition from correlated to uncorrelated electron-hole pair recombination, and the complex carrier dynamics in these systems.

The trigonal Weyl semimetal ${\mathrm{PtBi}}_2$ presents an intriguing superconducting phase, previously reported to be confined to its topological Fermi arcs within a certain temperature range. This observation highlights the importance of a thorough understanding of its normal phase, particularly the roles that spin-orbit coupling (SOC) and inversion-symmetry breaking play in shaping its band structure. Our density-functional theory calculations reveal that the semimetallic nature of trigonal ${\mathrm{PtBi}}_2$ can be interpreted as stemming from a noncentrosymmetric crystal distortion of a parent structure that drives a metal-to-semimetal transition. This distortion breaks inversion symmetry and, crucially, reduces translational symmetry. Due to its interplay with translational symmetry, inversion-symmetry breaking emerges as the dominant energy scale producing substantial asymmetries ($\sim 0.6$ eV) in certain short-range hopping amplitudes, superseding the effects of SOC, whose primary role is to define the characteristics of the low-energy nodal structure and of the topological Fermi arcs. This also applies to the formation of the Weyl nodes closest to the Fermi energy, which are found to exist even in the absence of SOC as a result of the orbital physics associated with the reduced translational symmetry.

Projective measurements are a key element in quantum physics and enable rich phenomena in monitored quantum dynamics. Here, we show that the measurement outcomes, recorded during monitored dynamics, can provide important information about the properties of the monitored dynamical system with prethermal nonergodicity. We demonstrate this for a Floquet model of many-body localization, where we find that the prethermal many-body localized regime becomes unstable against rare measurements, yielding an unusual enhancement of quantum entanglement. Through an unsupervised learning and mutual information analysis on the classical dataset of measurement outcomes, we find that the information loss in the system, reflected by the increased entanglement, is compensated by an emergent structure in this classical dataset. Our findings highlight the crucial role of measurements and corresponding classical outcomes in capturing prethermal nonergodicity, offering a promising perspective for applications to other monitored quantum dynamics.

We propose cyclotron resonance as an optical probe for emergent fractionalized excitations in $\mathrm{U}\left(1\right)$ quantum spin liquids, focusing on kagome antiferromagnets. In contrast to conventional systems, where cyclotron resonance directly couples to charged carriers, spinons in spin liquids are charge-neutral and interact only through an emergent gauge field, making direct probing challenging. We identify two key mechanisms by which an external physical electromagnetic field induces emergent electric and magnetic fields, enabling indirect coupling to spinons. Using these mechanisms, we compute the absorption rate of the cyclotron resonance response for Dirac spinons forming Landau levels. Our analysis shows that, although the absorption per layer is small, the absence of a skin-depth limitation in insulating spin liquids allows for cumulative absorption comparable to graphene in realistic sample sizes for the recently discovered spin-liquid candidate material ${\mathrm{YCu}}_3{\left(\mathrm{OH}\right)}_6{\mathrm{Br}}_2\left[\mathrm{Br}{}_{1-y}{\left(\mathrm{OH}\right)}_y\right]$. Our proposed cyclotron-resonance measurement is a decisive, practical test for spinon Landau levels, providing quantitative expectations where clear experimental evidence has so far been lacking.

A periodic lattice distortion that reduces the translational symmetry folds electron bands into a reduced Brillouin zone, leading to band mixing and a tendency to gap formation, as in the Peierls transition in one-dimensional systems. However, in higher dimensions, the resulting phase can present topological obstructions preventing a complete gap opening. We discuss two different mechanisms for such obstructions: emergent Weyl nodes and symmetry protected band crossings. Based on density-functional calculations, we show these mechanisms are at play in trigonal ${\mathrm{PtBi}}_2$.

We investigate generalized Aubry-André models featuring tunable quasidisordered potentials and a mobility edge that separates extended and localized states, with critical states for the mobility edge confirmed through finite-size scaling analysis. Numerical results demonstrate that extended, critical, and localized states can be distinguished via their phase-space representations, particularly the Wigner distribution. The associated Wigner entropy, derived from this distribution, peaks at the critical state, enabling precise localization of the mobility edge. Additionally, wave-packet dynamics reveal anomalous transport behaviors, including superdiffusion and subdiffusion, bridging ballistic transport and the absence of diffusion.

Intriguing ferroelectric (FE) polarization has been reported in various materials, where intrinsic symmetry-breaking characteristics and spin-orbit coupling (SOC) effect play a significant role. However, the mechanism underlying of the Rashba SOC manipulation ferroelectric properties under Br atomic displacement remains unclear. In this study, we employ hybrid functional and ab initio nonadiabatic molecular dynamics with SOC to elucidate the impact of Rashba SOC on the ferroelectricity and carrier spin dynamics in the FE $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2\mathrm{B}{\mathrm{r}}_9/\alpha \text{−}\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3\downarrow$ heterostructure with atomic displacement. The results reveal that the ferroelectricity can be significantly enhanced by Rashba SOC due to increased symmetry breaking. Remarkably, Br atomic displacement modulation leads to enhancement in both ferroelectric polarization $\left(0.69\mu \mathrm{C}/\mathrm{c}{\mathrm{m}}^2\right)$ and spin-splitting strength (${\alpha }_{\mathrm{R}}=1.18\mathrm{eV}/\AA$). Spin splitting occurs at the conduction band minimum of heterostructure, where carriers in same-spin channels relax primarily through electron-phonon coupling. The relaxation process is dominated by spin-down carriers, with electron and hole relaxation time differences being five times larger than spin-up carriers (twice times). Notably, interfacial electron-hole recombination time accelerates to 122.78 fs under $\mathrm{\Delta }{d}_{\mathrm{Br}\text{−}\mathrm{Bi}}=0.008\AA$, significantly improving carriers' separation efficiency. Furthermore, we demonstrate that the spin photocurrent in the $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2\mathrm{B}{\mathrm{r}}_9/\alpha \text{−}\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3\downarrow$ heterostructure also can be effectively modulated by ferroelectric polarization. These findings advance the fundamental understanding of ferroelectric perovskite materials.

The discovery of high-temperature superconductivity in layered nickelates under pressure has recently triggered enormous interest. Studies of these compounds have revealed a density-wave-like transition at ambient pressure, though its connection with superconductivity is still not well understood. Here, we report a detailed $\mathrm{\mu }\mathrm{SR}$ study on single crystals of trilayer nickelate ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ at ambient pressure. We have identified a spin-density-wave (SDW) transition at the temperature of $T_{\mathrm{N}}\sim 130\mathrm{K}$, as well as a broad crossover around 70–100 K. Based on the temperature dependence of the muon precession amplitudes and magnetic susceptibility, we attribute this additional crossover either to a spin reorientation, or to an inhomogeneous SDW ordering.

Realizing novel topological states in magnonic systems unlocks robust, low-power spin-wave devices. In this paper, we show that incorporating left-handed spin waves (antimagnons) fundamentally reorganizes band topology, and enables tunable spin-wave coupling and chirality. We proposed a two-dimensional Su-Schrieffer-Heeger-like model, the 2D-SSH4 chain, where dipolar interactions between magnons and antimagnons generate topological bands with nonzero Chern numbers. This framework explains the origin of topological surface states in ferromagnetic multilayers and shows they share the same topological origin as classic magnetostatic surface spin waves. Our model also offers a straightforward framework for designing more complex magnetic multilayers connected by dipolar interactions, such as antiferromagnetic/ferromagnetic multilayers. In these dipolar-coupled multilayers, both coherent and dissipative interlayer spin-wave couplings, together with the layer-resolved chirality, are tunable via external magnetic fields and spin torques. Our results provide a practical platform for topological magnonics, enabling control of magnon chirality and coupling in future devices.

Misfit layer compound composed of alternately stacked rock-salt and transition metal dichalcogenides layers has attracted attention as a platform to study two-dimensional superconductivity. We successfully synthesized (${\mathrm{SnS})}_{1.15}({\mathrm{TaS}}_2$) single crystal and performed magnetic susceptibility measurements to reveal the superconducting properties. The lower and upper critical fields in the directions parallel and perpendicular to the layers are consistent with the GL description. The latter has a linear dependence on temperature, indicating (${\mathrm{SnS})}_{1.15}({\mathrm{TaS}}_2$) being an anisotropic three-dimensional superconductor. The hysteresis loop of the magnetization curve is observed in all three directions. The vortex pinning appears to be significant for the motion along the incommensurate axis, reflecting the crystalline structure.

Anharmonic effects are widely believed to be the primary cause of the overestimation of superconducting transition temperatures of yttrium hydrides ${\mathrm{YH}}_6$ and ${\mathrm{YH}}_9$ in theoretical predictions. However, prior studies indicate that anharmonicity alone may be insufficient to account for this discrepancy. In this work, we employ the stochastic path-integral approach to investigate the quantum and anharmonic effects of ions in yttrium hydrides. Our calculations reveal significant corrections to the electron-phonon coupling parameters and an increase in the average phonon frequency compared to density functional perturbation theory, aligning closely with results from the stochastic self-consistent harmonic approximation. We find that properly taking into account the renormalization of the Coulomb pseudopotential due to the frequency cutoff, which is often overlooked in previous calculations, is critical to predicting transition temperatures consistent with experimental values for both ${\mathrm{YH}}_6$ and ${\mathrm{YH}}_9$. This indicates that, with this correction, anharmonic effects are sufficient to explain the discrepancies between experimental and theoretical results.

Nonlinear optical (NLO) phenomena play a pivotal role in materials research and technological advancements, particularly for optoelectronic modulation and advanced photonic devices. Accurate evaluation of intrinsic NLO responses is crucial for targeted material discovery and performance optimization. However, conventional NLO coefficients (${\chi }_{ijk}^{\left(2\right)})$ exhibit strong bandgap ($E_g$) dependence, fundamentally distorting their correlation with actual conversion efficiency (η). This limitation not only impedes fair performance comparisons across materials with different $E_g$ values but also artificially amplifies the NLO capabilities of narrow-$E_g$ systems. To address this critical challenge, we propose an intrinsic NLO metric ${\phi }_{ijk}={\delta }_{ijk}·{{\chi }_{ii}}^{\left(1\right)}$, incorporating a static Miller dispersion correction (${\delta }_{ijk}$) that enables cross-$E_g$ evaluations and reveals structural limits of achievable η through fundamental parameter optimization. Our first-principles calculations, performed using our in-house NLOtools, demonstrate the advantage of ${\phi }_{ijk}$ over ${\chi }_{ijk}^{\left(2\right)}$ in decoupling $E_g$ effects while establishing a robust framework for rational design. This framework is demonstrated through the rational design of ${\mathrm{KCuMoS}}_4$, where targeted skeletal reconstruction and elemental substitution yielded a superior intrinsic NLO potential, confirmed by its concurrently high ${\phi }_{ijk}$ and normalized ${\mathrm{\Phi }}_{ijk}$ values. The favorable performance of ${\mathrm{KCuMoS}}_4$ illustrates a route to mitigating the classic trade-off between ${\chi }_{ijk}^{\left(2\right)}$ and $E_g$, providing a practical methodology for the rational design of high-performance NLO materials.

Multifold fermions, quasiparticles with multiple degeneracy protected by crystalline symmetries, exhibit a variety of intriguing phenomena stemming from their large topological charges and unique band structures. A comprehensive understanding of their response to external stimuli remains challenging, especially for types protected by nonsymmorphic symmetries where degrees of freedom, such as orbital, spin, sublattice, and crystal momentum, are intricately coupled. Here, we systematically construct effective models for multifold fermions that incorporate external fields based on crystalline symmetry. Specifically, we develop a $\mathit{k}·\mathit{p}$ model for the threefold fermion protected by space group $I{2}_1{31}^{\prime }$ (No. 199) in the presence of spin-orbit coupling and derive the terms for external fields. By complementing this with a tight-binding model, we investigate the magnetic field response and reveal the pair annihilation of magnetic monopoles. Furthermore, we construct a $\mathit{k}·\mathit{p}$ model for the eightfold fermion in space group $P\overline{4}3n{1}^{\prime }$ (No. 218), including its coupling to external fields. This work provides a robust theoretical foundation for advancing the study of external field responses and transport phenomena in multifold fermions, opening new avenues to explore their rich physics.

A mechanism for amplification of weak quadrupole transitions of Rydberg excitons in ${\mathrm{Cu}}_2\mathrm{O}$ by a plasmonic nanostructure is investigated. The theoretical description of exciton-plasmon interaction is presented and a field averaging approximation is proposed for calculations involving large excitons. Various types of copper, silver and gold-based plasmonic nanostructures are considered and their potential for enhancing quadrupole transitions is evaluated. The change of eigenstates and eigenenergies as the exciton approaches the semiconductor-metal interface is also analyzed.

We investigate anomalous planar transport phenomena in a recently identified class of collinear magnetic materials known as $d$-wave altermagnets (AMs). The anomalous planar effects manifest in a configuration when the applied electric field/temperature gradient, magnetic field, and the measured Hall voltage are all coplanar, but the planar magnetic field is instrumental in breaking ${\widehat{C}}_{4z}\widehat{\mathcal{T}}$ symmetry of the $d$-wave AM, where $\widehat{\mathcal{T}}$ is the time-reversal operator, resulting in a Zeeman gap at a shifted Dirac node and a nonzero Berry curvature monopole. We demonstrate that these systems exhibit nearly half-quantized anomalous planar Hall and planar thermal Hall effects at low temperatures that persist over a range of magnetic fields. The angular dependence of the planar transport reveals a $cos2\varphi$ dependence on the magnetic field direction, where $\varphi$ is the azimuthal angle made by the magnetic field. We also discuss the anomalous planar Nernst effect, or transverse thermopower, and demonstrate that the Nernst conductivity peaks when the chemical potential lies just outside the induced Zeeman gap and vanishes within the gap. We further explore the dependence of all three coefficients on the polar and the azimuthal angle of the magnetic field when it is rotated in the full three-dimensional space. Our results reveal the presence of an approximately half-quantized anomalous planar thermal Hall plateau for a range of in-plane magnetic fields without requiring topological superconductivity and conducting Majorana modes, which can be probed in experiments in $d$-wave AMs.

Conservation laws serve as the hallmark of integrability. The absence of conserved charges typically implies that the model is nonintegrable. The recently proposed Fredkin spin chain exhibits rich structures, and its ground state is analytically known. However, whether the Fredkin spin chain is integrable remains an open question. In this work, through rigorous analytical calculations, we demonstrate that the Fredkin spin chain, under both periodic and open boundary conditions, lacks local conserved charges, thereby confirming its nonintegrable nature. Furthermore, we find that when one or a portion of the Hamiltonian terms are removed (referred to as the truncated Fredkin spin chain), local conserved charges are still absent. Our findings suggest that in models involving three-site interactions, integrable models are generally rare.