Driving nontopological materials out of equilibrium using time-periodic perturbations, such as circularly polarized laser light, is a compelling way to engineer topological phases. At the same time, topology has traditionally only been considered for crystalline materials. Here we propose an experimentally feasible way of driving monolayer amorphous carbon topological. We show that circularly polarized laser light induces both regular and anomalous edge modes at quasienergies 0 and $\pm \pi$, respectively. We also obtain a complete topological characterization using an energy- and space-resolved topological marker based on the spectral localizer. Additionally, by introducing atomic coordination defects in the amorphous carbon, we establish the importance of the local atomic coordination in topological amorphous materials. Our work establishes amorphous systems, including carbon, as a versatile and abundant playground to engineer topological phases.

Magnetic skyrmioniums, possessing zero net topological charge, are promising candidates for next-generation spintronic devices. Using micromagnetic simulations, we investigate the current-driven dynamics of ferromagnetic (FM) and synthetic antiferromagnetic (SAF) skyrmioniums in granular nanotracks. Local variations in interfacial Dzyaloshinskii–Moriya interaction, anisotropy, and saturation magnetization are found to strongly influence skyrmionium mobility and stability. FM skyrmioniums exhibit pronounced sensitivity to disorder, showing pinning at low current densities and Magnus force induced deformation at high current densities. Their mobility is strongly dependent on grain size: smaller grains promote smoother motion, while larger grains enhance pinning. Moreover, an external magnetic field is found to enhance FM skyrmionium stability by mitigating transverse distortions. In contrast, SAF skyrmioniums display remarkable robustness across a wide range of disorder strengths and current densities due to the cancellation of the Magnus force, maintaining higher longitudinal velocities. Disorder-induced pinning forces hinder the longitudinal motion of both FM and SAF skyrmioniums by introducing energy barriers that suppress their velocity, however, the effect of disorder is weaker for SAF skyrmioniums. These findings establish SAF skyrmioniums as robust, disorder-tolerant candidates for next-generation racetrack memory and spintronic logic devices.

Rare-earth tri-iodides ($R{\mathrm{I}}_3$) are a series of two-dimensional van der Waals (vdW) magnetic materials comprising a layered honeycomb structure. Both the growing interest in vdW magnetic systems and the honeycomb layered structure of $R{\mathrm{I}}_3$ compounds, which is essential for realizing Kitaev physics, motivated us to grow high-quality single crystals of this series of materials and investigate their ground-state magnetic properties. Here, we report the crystal growth, magnetic, and thermodynamic properties of large (centimeter-sized), high-quality crystals of $R{\mathrm{I}}_3$ compounds. The crystal growth uses the physical vapor transport method via self-transport reaction using iodine as a transporting agent. The growth parameters are meticulously reported. The crystallographic parameters are obtained using single-crystal x-ray diffraction. While the $R{\mathrm{I}}_3$ compounds for the lighter rare earths ($R$ = La and Ce) crystallize with an orthorhombic (Cmcm) structure, the structure for the heavier rare earths is trigonal ( $R\overline{3}$ ), analogous to the extensively investigated Kitaev material $\alpha \text{−}{\mathrm{RuCl}}_3$. The density functional theory–based calculations are performed to obtain the eigenfrequencies/eigenvectors of the Raman-active phonon modes for both structure types and compared with the experimental Raman spectra of ${\mathrm{CeI}}_3$ (Cmcm) and ${\mathrm{HoI}}_3$ ( $R\overline{3}$ ). The magnetic behavior examined for the heavier rare-earth-based compounds indicates no signs of long-range magnetic ordering down to 2 K. However, signatures of short-range correlations are seen below 5 K, both in the magnetic susceptibility and specific heat of all the compounds.

We present a systematic investigation of superconductivity in a topological superconductor candidate $T_d{\text{-MoTe}}_2$ in the few-layer limit. By examining multiple mechanically exfoliated samples with different thicknesses, substrates, and crystal qualities, we quantitatively correlate superconducting temperature $\left(T_c\right)$ with disorder, carrier density, carrier type, and mobility. By integrating these experimental findings with first-principles calculations, we reveal the relationship between the band structure and superconductivity in this material. Notably, in two-layer samples we access a highly hole-doped regime that has not been systematically explored in previous experiments, providing a complementary perspective to earlier studies. In this regime, we demonstrate that superconductivity can be realized in a manner consistent with a conventional phonon-mediated $s_{(++)}$-wave pairing.

Topological nodal superconductors (SCs) have attracted considerable interest due to their gapless bulk excitations and exotic surface states. In this paper, by establishing a general framework of the effective theory for multiorbital SCs in the weak-pairing limit, we realize a class of three-dimensional time-reversal ($\mathcal{T}$) invariant Dirac SCs, with their topologically protected gapless Dirac nodes being located at generic momenta. By introducing $\mathcal{T}$-breaking pairing perturbations, we demonstrate the existence of Majorana hinge modes in these Dirac SCs as evidence of their realization of higher-order topology. We also propose a kind of $\mathcal{T}$-breaking Dirac SCs, whose Dirac nodes possess nonzero even chiralities and so are characterized by surface Majorana arcs.

We establish the integrability of a family of Sachdev-Ye-Kitaev (SYK) models with uniform $p$-body interactions. We derive the R-matrix and mutually commuting transfer matrices that generate the Hamiltonians of these models, and obtain their exact eigenspectra and eigenstates. Remarkably, the R-matrix is that of the critical transverse-field Ising chain. This work reveals an unexpected connection between the SYK model, central to many-body quantum chaos, and the critical Ising chain, a cornerstone of statistical mechanics.

We investigate the transport properties of the interface between normal and superconducting Weyl semimetals. We find that the Fermi arcs on the junction interface consist of two types of arc fragments: localized Fermi arcs, composed of states entirely confined to the interface, and resonant Fermi arcs, formed by states partially localized at the interface. The existence of these interface resonant states arises from the interaction between interface Fermi arcs and superconductivity. These resonant states induce an Andreev reflection anomaly, where Andreev reflection is significantly enhanced and its probability reaches unity at a specific momentum space point where the resonant states merge into the bulk continuum. The Andreev reflection anomaly generates an additional supercurrent, which becomes most pronounced when the incident Fermi pocket is tangent to the transmissive one.

We provide insights into the atomistic details of the ultrafast spatially resolved breakdown of the insulating ${\mathrm{M}}_1$ phase in bulk ${\mathrm{VO}}_2$ employing an ab initio technique based on dynamical mean-field theory and time-dependent density-functional theory. We find that the system is initially metallized preferentially along the vanadium-dimer chains, with a subsequent growth of metallic bubbles elongated along the ${\mathrm{C}}_{\mathrm{R}}$ direction. We trace the breakdown of the insulating phase to the two types of oxygen atoms resulting from vanadium dimerization, which produces a nontrivial charge-density modulation in the oxygen-atom chains with significant charge transfer to the interdimer bond. These results, which are in qualitative agreement with experimental data, shed light on the important role of the nonequivalent oxygen atoms in the spatially resolved ultrafast response of this strongly correlated insulator.

When an electron beam is incident from a Weyl semimetal (WSM) onto another material and undergoes reflection, it exhibits a spatial shift. This shift depends on the in-plane wave vectors and displays vortex structures in the incident pocket (the projection of the Fermi surface) or on the pocket edge. According to Yang and He [Phys. Rev. B 110, 195302 (2024)], based on the quantization of Berry flux on the Fermi surface of a type-I WSM, the total vortex number corresponds to the topological charge carried by the Weyl point, while the number of edge vortices equals that of the Fermi arcs connected to the incident pocket. However, when the incident material is a type-II WSM, the Fermi surface of incidence is a hyperboloid (the Fermi pocket is a two-sheeted hyperbola), which is fragmental and nonenclosed. In this case, the quantization condition breaks down and the definition of interface topology requires revision. We introduce a composite loop for the incident sheet comprising two segments: one tracing the sheet edge and the other winding back across the hyperbola in the remote. It is found that the accumulation of reflection shift along the composite loop serves to characterize the interface topology. The edge segment yields both the number of edge vortices and that of Fermi arcs connected to the incident sheet, whereas the crossing segment counts the lost vortices—those absent in the open Fermi surface but expected in a closed one. A vortex loss in one sheet mandates the emergence of an antivortex in the other. Our findings enrich the understanding about topological properties of materials with open Fermi surfaces.

Intermetallic compounds such as ${\mathrm{A}}_2{\mathrm{B}}_7$ alloys are promising candidates for mobile hydrogen storage applications due to their high and reversible hydrogen absorption capacity. We compute the absorption isotherm of ${\mathrm{Nd}}_3{\mathrm{MgNi}}_{14}$ from first principles using a multiscale modeling approach. Absorption sites are identified through a systematic geometrical analysis, and are characterized with density functional theory (DFT) calculations. The absorption site properties are used in room-temperature grand canonical Monte Carlo simulations to predict hydrogen uptake as a function of pressure, leading to a full absorption isotherm in good agreement with experimental data. We show that both hybrid exchange-correlation functionals and zero-point energy corrections are necessary to obtain accurate absorption properties. The analysis of the fully hydrogenated structure with DFT shows considerable volume expansion, which stabilizes the structure at large hydrogen content.

Topological Anderson insulators represent a class of disorder-induced, nontrivial topological states of matter. In this study, we propose a feasible strategy to unveil and design topological Anderson insulators protected by latent symmetries. These are not visible in the original system, but become obvious after performing an isospectral reduction. Using this technique, we design a family of disordered multiatomic chains that exhibit latent chiral symmetry or mirror (inversion) symmetry. Using topological invariants, bulk polarization, and the divergence of localization length of the topological bound edge states in the reduced disordered system, we show how to identify the gapped and ungapped topological Anderson states in the original systems. Our work thus extends the concept of topological Anderson insulating phases protected by geometric symmetries and tenfold-way classification to the various types of latent symmetry cases. Overall, our work paves the way for exploiting topological Anderson insulators in terms of latent symmetries.

While twisted magnonic crystals (MCs) have recently gained attention for their intriguing linear phenomena, such as magnon flat bands, their nonlinear dynamics—particularly the generation of magnonic frequency combs (MFCs)—have remained largely unexplored. In this work, we demonstrate the creation of MFCs in twisted MCs using two-tone microwave excitation. We find that finite twist angles significantly enhance three-magnon interactions, driven by the noncollinear ground-state magnetic configuration induced by interlayer dipole-dipole interactions. The coupling strength of three-magnon interactions exhibits a plateau-like dependence on the twist angle. Moreover, the magnon band structure is modified by twisting, resulting in band gaps diminishing and even vanishing at certain angular ranges. The combination of the two unique roles of twisting reveals an optimal range of twist angles for achieving high-quality MFCs with a large number of comb teeth. Our findings deepen the understanding of nonlinear interactions in twisted MCs and highlight their potential for advancing moiré-based materials in information processing and high-precision metrology.

The altermagnet (AM), characterized by zero net magnetization combined with momentum-dependent spin polarization, is regarded as a new type of collinear magnet and has attracted increasing interest since the fundamental concept of altermagnetism was established. Although many AM candidates have been theoretically proposed, most experimentally confirmed AM candidates are semiconductors. More recently, a metallic AM candidate of the bulk ${\mathrm{KV}}_2{\mathrm{Se}}_2\mathrm{O}$ was experimentally identified to have Fermi surface and altermagnetic spin splitting features. It is anticipated that the two-dimensional (2D) monolayer counterpart can be fabricated by mechanical exfoliation of the ${\mathrm{KV}}_2{\mathrm{Se}}_2\mathrm{O}$ bulk compound. Here, we present our first principles calculations to demonstrate that the corresponding 2D ${\mathrm{K}}_2{\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$ monolayer has an increased lattice constant and excellent stability at room temperature. Most importantly, the ${\mathrm{K}}_2{\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$ monolayer manifests as an altermagnetic semiconductor with an out of plane magnetization axis and its Néel temperature is approximately 580 K. The exfoliation of the ${\mathrm{KV}}_2{\mathrm{Se}}_2\mathrm{O}$ bulk into the ${\mathrm{K}}_2{\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$ monolayer probably leads to the 2D AM semiconductor consisting of spin-valley locking at the $X$ or $Y$ valley. It is anticipated that a giant piezovalley effect of 0.15 eV valley polarization can be obtained by using a 2% anisotropic strain to break the diagonal mirror symmetry. Our findings provide a promising AM candidate for valleytronics and spintronics at room temperature.

We report a comprehensive investigation of the physical properties of single crystals of Dirac semimetal EuAuBi, using neutron diffraction, magnetization, electrical transport, and specific heat measurements. EuAuBi crystallizes in a hexagonal structure with space group $P{6}_{3}mc$ (no. 186). First-principles calculations using density functional theory characterize it as a Dirac semimetal, with a notable band crossing in proximity to the Fermi level ($E_{\mathrm{F}}$) along the $\mathrm{\Gamma }$-A direction. The crystal exhibits three distinct magnetic phases at 4 K ($T_{\mathrm{N}1}$), 3.5 K ($T_{\mathrm{N}2}$), and 2.8 K ($T_{\mathrm{N}3}$) as observed from magnetic and specific heat measurements. However, zero-field neutron diffraction resolves only two magnetic phases: a commensurate antiferromagnetic phase and a canted antiferromagnetic phase. Field-dependent ac and dc magnetization measurements uncover field-induced nontrivial spin textures in the magnetic field range 1.5 to 3 T, manifested as a tilted plateau in the magnetization curves. The interplay between conduction carriers and these spin textures is further evidenced by unique features in the magnetic field-dependent longitudinal resistivity. Finally, we present a comprehensive magnetic phase diagram of EuAuBi, highlighting diverse spin alignments present in the material. EuAuBi thus emerges as a rare material system in which both momentum-space and real-space Berry curvature effects may coexist, providing a unique opportunity to investigate their interplay.

We investigate the ultrafast magnetization dynamics of semiconducting antiferromagnetic CrSBr using real-time time-dependent density functional theory. In zero magnetic field, laser excitation modifies only the magnetization along the easy axis, leaving transverse components unaffected. We find that below-gap, low-fluence pulses enhance the local magnetic moments via spin transfer from nonmagnetic to magnetic atoms, increasing the Néel vector. In contrast, high-fluence pulses drive interlayer spin transfer between magnetic atoms, producing strong demagnetization and reducing the Néel vector, while S and Br atoms exhibit primarily charge transfer with weak opposite contribution to the demagnetization. An applied magnetic field qualitatively alters the response, enabling both magnitude changes and ultrafast reorientation of the magnetization. We show that the resulting layer-resolved reorientation respects a twofold rotation about the $x$ axis, exciting coherent optical magnons even under this symmetry, which modulate the relative angle between neighboring layers and periodically tune electronic properties. These results reveal a microscopic pathway for coherent magnon excitation in van der Waals magnets and establish a framework for controlling their coupled spin-charge dynamics on femtosecond timescales.

Layered materials are promising candidates for spintronic applications due to their unique electronic structures and spin transport properties. However, the strong anisotropic conductivity inherent in these materials complicates the quantitative evaluation of spin Hall conductivity and spin diffusion length. In this work, we present a comprehensive study of spin transport in a transition metal dichalcogenide ${\mathrm{PtTe}}_2$ by combining a three-dimensional finite element model with nonlocal spin valve structures. We developed a theoretical model that treats an anisotropic spin diffusion in the same way as the conventional isotropic model, enabling the extraction of spin diffusion lengths along both the in-plane and out-of-plane directions. Our analysis revealed that the conventional isotropic assumption tends to overestimate some values, particularly for the out-of-plane spin diffusion length and spin Hall conductivity. These findings provide new insight into anisotropic spin diffusion and spin-charge conversions in layered materials and emphasize the importance of accounting for anisotropic conductivity in the design of spintronic devices.

We discuss the possible topological order/topological quantum field theory of different quantum Hall systems. Given the value of the Hall conductivity, we constrain the global symmetry of the low-energy theory and its anomaly. Specifically, the one-form global symmetry and its anomaly are presented as the organizing principle of these systems. This information is powerful enough to lead to a unique minimal topological order (or a small number of minimal topological orders). Almost all of the known experimentally discovered topological orders are these minimal theories. Since this work is interdisciplinary, we made a special effort to relate to researchers with different backgrounds by providing translations between different perspectives.