Sliding is a ubiquitous phenomenon in moiré systems, but its direct influence on moiré bands, especially in multitwist moiré systems, has been largely overlooked to date. Here, we theoretically show that sliding provides a unique pathway to engineer the quantum geometry (Berry curvature and quantum metric) of moiré bands, exhibiting distinct advantages over conventional strategies. Specifically, we first suggest alternating twisted trilayer ${\mathrm{MoTe}}_2$ (AT3L-${\mathrm{MoTe}}_2$) and chirally twisted triple bilayer graphene (CT3BLG) as two ideal paradigmatic systems for probing sliding-engineered quantum geometric phenomena. Then, two sliding-induced exotic quantum geometry phenomena are predicted: (1) an intrinsic nonlinear Hall effect via sliding-produced nonzero Berry curvature dipole, with CT3BLG as an ideal platform, and (2) significant quantum metric modulation in AT3L-${\mathrm{MoTe}}_2$, enabling tests of quantum geometric criteria for the fractional Chern insulating state. Our work establishes sliding as a degree of freedom for manipulating quantum geometry of moiré bands, which emerges as a signature phenomenon of multitwist moiré systems.

The effects of one-dimensional hydrogen on the ferroelastic transition and elasticity of stishovite are determined up to 52.5 GPa using x-ray diffraction, Raman spectroscopy, and first-principles calculations. In contrast to the well-studied hydrogen-free stishovite or that with hydrogarnetlike point defects, stishovite with hydrogen intercalation develops into the ${\mathrm{CaCl}}_2$-type phase at a remarkably low pressure of 3.3 GPa, but the shear instability is postponed to 17.3 GPa. We rationalize the decoupling of the ferroelastic transition by modeling the spontaneous strains using Landau theory, and reveal a two-stage hierarchical progression of lattice distortion. Strains are originated from ${\mathrm{SiO}}_6$ octahedra surrounding the channel-like hydrogen defects, then subsequently propagate to bulk lattice with increasing pressure. Despite being the lightest atom and x-ray invisible, the elastic properties of stishovite are highly sensitive to the hydrous defect. Hydrogen-bearing stishovite may therefore induce shear anomalies in hydrous slabs at much shallower mantle depths than previously thought.

The magnetic moment in van der Waals (vdW) materials containing $3d$ transition metals originates from unpaired $d$-electron spins and their interaction with surrounding ligands. The interplay between exchange interactions and magnetic anisotropy stabilizes long-range ordering of such moments. The compound ${\mathrm{CuCrP}}_2{\mathrm{S}}_6$ (CCPS) presents an interesting class of vdW solids where the coupling of $\mathrm{C}{\mathrm{r}}^{3+}$ moments and ordering of $\mathrm{C}{\mathrm{u}}^{1+}$ ions give rise to a multiferroic ground state. Here we investigate the spin dynamics of $\mathrm{C}{\mathrm{r}}^{3+}$ ions in CCPS through magnetization and broadband as well as single sub-THz magnetic resonance measurements. The orbital moment of $\mathrm{C}{\mathrm{r}}^{3+}$ is quenched under the octahedral crystal field of surrounding chalcogen ions, resulting in negligible magnetic anisotropy—a feature common to Cr-based vdW antiferromagnets (AFM). Resonance spectra over a wide frequency-field-temperature range reveal quasi-2D AFM dynamics governed mainly by isotropic Cr-Cr exchange interactions, which determine the magnetic order, spin reorientation, and damping. Sub-THz resonance spectra also uncover a field-induced ferromagnetic polarization, highlighting the universal role of Cr-Cr exchange in layered Cr compounds. Moreover, persistent magnetic correlations far above the Néel temperature ($T_{\mathrm{N}}\approx 32\mathrm{K}$) points to a short-range magnetic order in CCPS and motivate future studies of a possible interplay between AFM and antiferroelectric orders. These results establish CCPS as an exemplary system for exploring 2D magnetism and electric-field-tunable spintronic functionalities in layered multiferroics.

Quasiparticle hybridization remains a major challenge in realizing and controlling exotic states of matter in existing quantum simulation platforms. We report the absence of hybridization for compact localized states (CLSs) emerging in the chiral spin liquid described by the Yao-Kivelson model. The CLS forms due to destructive quantum interference at fine-tuned coupling constants and populates perfectly flat quasiparticle bands on an effective kagome lattice. Using a formalism for general Majorana-hopping Hamiltonians, we derive exact expressions for CLSs for various flux configurations and both for the topological and trivial phases of the model. In addition to finite-energy matter fermions with characteristic spin-spin correlations, we construct compact localized Majorana zero modes attached to $\pi$-flux excitations, which enable non-Abelian braiding of Ising anyons with minimal separation. Our results inform the quantum simulation of topologically ordered states of matter and open avenues for exploring flat-band physics in quantum spin liquids.

The ${\mathrm{NiBi}}_3$ compound exhibits a compelling interplay between superconductivity and magnetism, further enriched by topological characteristics that make it an exceptional platform for exploring emergent electronic phenomena. Here, we report experimental evidence of unconventional magnetic phenomena in high-quality single crystals of ${\mathrm{NiBi}}_3$, revealed through detailed magnetotransport measurements. The magnetoresistance increases with temperature, featuring two distinct behaviors, a classical ordinary component at high fields and a linear contribution at low magnetic fields. In addition, anomalous Hall effect signals persist down to the superconducting transition temperature and vanish at 150 K. These observations suggest that magnetic fluctuations play a significant role in charge transport in ${\mathrm{NiBi}}_3$, highlighting the influence of magnetic correlations and strong spin-orbit coupling in the electronic structure. Our findings underscore the complex and multifaceted nature of this material.

Boron carbide is a material of choice for multiple industries, e.g., aerospace, as a lightweight structural ceramic due to its high hardness, high melting temperature, and low density. However, its mechanical properties have been observed to radically degrade under shockwave compression, presumably as a consequence of stress-induced phase transitions resulting in its partial amorphization. So far, the physical mechanism underpinning this behavior remains unclear. Here, we report a pressure-induced phase transition in boron carbide occurring between 78 and 90 GPa during static compression in diamond anvil cells, both at room temperature and after quenching from high temperatures. The crystal structure of the new phase was solved and refined via synchrotron single-crystal x-ray diffraction measurements and further investigated by Raman spectroscopy as well as density functional theory calculations. The discovered high-pressure polymorph, $\mathit{mC}60\text{−}{\mathrm{B}}_{13}{\mathrm{C}}_2$, has strong resemblance with the known ambient conditions phase, $\mathit{hR}45\text{−}{\mathrm{B}}_{13}{\mathrm{C}}_2$, with the important distinction that the linear C–B–C chain linking ${\mathrm{B}}_{12}$ icosahedra in $\mathit{hR}45\text{−}{\mathrm{B}}_{13}{\mathrm{C}}_2$ is bent in $\mathit{mC}60\text{−}{\mathrm{B}}_{13}{\mathrm{C}}_2$. Such bending of the C–B–C chain has been hypothesized as key to explain boron carbide's drop in strength, phase transitions, and amorphization. The observed reversibility of the phase transition, as well as the formation of covalent bonds between ${\mathrm{B}}_{12}$ icosahedra and the bent C–B–C chains, are assessed to decipher the C–B–C chain's bending importance on the amorphization and mechanical properties of boron carbide.

We study the mode dynamics of a generic quadratic fermionic Hamiltonian under a sudden quench protocol in momentum space. Modes with zero energy at any given time, $t$, are referred to as dynamical critical modes. Among all zero-energy modes, spin-flip symmetry is restored in the eigenvector corresponding to selected zero-energy modes. This symmetry restoration is used to define the dynamical quantum phase transition (DQPT). This shows that the occurrence of these dynamical critical modes is necessary but not sufficient for a DQPT. We show that the conditions on the quench protocol and time for such dynamical symmetry restoration are the same as the divergence of the rate function and integer jump in the dynamical topological order parameter, which have been the traditional identifiers of a DQPT. This perspective also naturally explains when one or both of DQPT and ground-state quantum phase transitions will occur.

Governed by specific symmetries, altermagnetism is an emerging field in condensed matter physics, characterized by unique spin-splitting of the bands in the momentum space coexisting with the compensated magnetization as in antiferromagnets. As crystals can have tailored and unintended defects, it is important to gain insights on how altermagnets are affected by the defects-driven symmetry-breaking which, in turn, can build promising perspectives on potential applications. In this study, considering the widely investigated MnTe as a prototype altermagnet, defects are introduced through substitutional doping to create a large configuration space of spin space groups. With the aid of density functional theory calculations, symmetry analysis, and model studies in this configuration space, we demonstrate the generic presence of spin-split of the antiferromagnetic bands in the momentum space. This is indicative of a wider class of quasi-altermagnetic materials, augmenting the set of ideal altermagnetic systems. Furthermore, we show that while pristine MnTe does not show anomalous Hall conductivity (AHC) with out-of-plane magnetization, suitable doping can be carried out to obtain finite and varied AHC. Our predictions of quasi-altermagnetism and doping-driven tailored AHC have the potential to open up as-yet-unexplored directions in this developing field.

Symmetry breaking is identified as a predominant mechanism governing the formation of exotic quantum state. The absence of inversion symmetry in noncentrosymmetric superconductors leads to an antisymmetric spin-orbit coupling, which promotes the system toward possible unconventional electron pairings. In this work, we present angle-resolved magnetotransport measurements on noncentrosymmetric $4H_{\mathrm{a}}\text{-NbS}{\mathrm{e}}_2$ single crystal with $T_{\mathrm{CDW}}\sim 40\mathrm{K}$ and $T_{\mathrm{c}}\sim 6.4\mathrm{K}$, to further shed light on the underlying mechanisms responsible for the Pauli-limit-violated and in-plane anisotropic superconductivity in transition metal dichalcogenides. Our results reveal that the broken inversion symmetry generates Zeeman-like spin-orbit coupling which induces spin-momentum locking. As a result, the in-plane upper critical field exceeds the Pauli limit, which evidences the existence of an Ising pairing state. We surprisingly note that upper critical field manifests a distinct twofold modulation when the magnetic field is rotated in the basal plane. The twofold symmetric superconductivity spontaneously breaks the threefold rotational symmetry of the crystal lattice, indicating nematic superconductivity in this bulk Ising superconductor.

The enhancement of superconductivity at surfaces and interfaces, where the order parameter persists at higher temperatures or magnetic fields than in the bulk, is a subtle yet fundamentally important phenomenon in condensed matter physics. In this work, we experimentally investigate the difference between near-surface and bulk superconducting transitions in 160-nm-thick NbN films, a conventional $s$-wave superconductor, under magnetic fields up to 8 T. To this end, we developed a highly sensitive nonlocal four-probe measurement scheme capable of simultaneously detecting surface and bulk electrical responses. This approach revealed distinct critical temperatures and superconducting transition widths that vary with the orientation of the applied magnetic field, ranging from perpendicular to parallel to the film plane. Our findings are consistent with recent theoretical predictions concerning multiple phase transitions in superconductors with spin-imbalanced fermion populations. The results not only establish a robust methodology for probing boundary-induced superconducting phenomena, but also provide insights relevant to the design of superconducting devices with engineered surface properties.

The sign-problematic generalized Baxter-Wu (GBW) model with asymmetric complex couplings is mapped onto a one-dimensional quantum model. Utilizing the model's exactly known critical properties, we study the relation between the conventional and the modified average signs and the phase transitions in the GBW model. We find that the average sign develops a negative peak near the critical point, but it is not a unique indicator of phase transition, as similar features can appear in noncritical regions. While the average modified sign provides a viable probe for the phase transition, the practical effectiveness of this method is limited by the exponential scaling of computational cost with the system's volume. We propose that the universal properties of the original model can be investigated through simulating the related reference model, based on the universality assumption. Using finite-size scaling analysis based on Monte Carlo simulations, we confirm the validity of this method, which thereby provides a novel framework for investigating phase transitions in systems plagued by the sign problem.

Nodal-sphere semimetals (NSSMs), featuring spherical band degeneracies in momentum space, constitute a fascinating class of topological materials. However, their realization in real materials is severely hampered by discrete crystallographic symmetry constraints, often resulting in gapped “pseudo” nodal spheres. Here, combining first-principles calculations and symmetry analysis, we predict a new three-dimensional boron allotrope, ${\text{CT-B}}_{24}$, as a nearly ideal NSSM. Its structural stability is systematically confirmed by phonon calculations, ab initio molecular dynamics simulations at 600 K, and elastic constant analysis. Notably, the electronic structure of ${\text{CT-B}}_{24}$ exhibits two bands crossing linearly near the Fermi level, forming a quasinodal sphere around the $\mathrm{\Gamma }$ point. The maximum energy gap is merely 0.008 meV, which is two orders of magnitude smaller than the gaps reported in previous pseudo-NSSMs. Furthermore, the (001) surface hosts pronounced drumheadlike surface states located outside the projected nodal sphere, providing distinct signatures detectable by angle-resolved photoemission spectroscopy. The nodal sphere also demonstrates remarkable robustness and tunability under external strain, driving a topological phase transition from an NSSM to a critical transition state and finally to a trivial insulator. Our work not only presents a superior material platform for exploring nodal-sphere physics but also suggests potential for strain-tunable topological devices.

In CuCl semiconductor microcavities with large decay of the cavity photon (CP), we have studied the dependence of the coupling energy between excitons and CPs on the position of the active layer in the cavity layer, using angle-resolved transmission (ART) spectroscopy. The ART spectra show that the characteristic energies and spectral widths of three cavity polariton branches depend on the incident angle of the probe light, and the spectral profiles of the respective branches also change between the symmetric and asymmetric structures. The incident-angle dependence of the characteristic energies and spectral widths of the respective branches extracted by the asymmetric spectral function is interpreted by the complex eigenvalues of the non-Hermitian effective Hamiltonian. This analysis in terms of an open quantum system allows us to estimate the coupling energy even in the weak coupling regime by considering the decay rates of CPs and excitons. From the analytical results, it is found that the coupling energies of the cavity polaritons depend on the position of the active layer, which indicates that the exciton-photon coupling changes between the strong and weak coupling regimes. Moreover, we discuss the active-layer position dependence of the coupling energy by considering the overlap integral of the exciton polarization and electric field of the CP.

We investigate the magnetotransport properties of a two-dimensional electronic system with unconventional Rashba spin-orbit coupling. We obtain the Landau levels analytically and find that intra-spin and/or inter-spin Landau-level crossing occurs. We compute the longitudinal conductivity and quantum Hall conductivity using the Kubo formalism based on linear response theory. We find that the usual Shubnikov-de Haas (SdH) oscillation in longitudinal conductivity appears, which is purely spin polarized, provided the Fermi level is placed suitably. Interestingly, we observe a beating pattern in the SdH oscillation in the intra-spin branches, which arises due to the superposition of SdH oscillations corresponding to two bands in each spin branch. This is contrary to the conventional Rashba system, where such beating is due to the superposition of SdH oscillation corresponding to two spin-branches. On the other hand, we note that quantum-Hall conductivity exhibits usual quantization in units of $e^2/h$. However, the Landau-level crossing gives rise to the double jump in the Hall conductivity if the Fermi level is placed precisely at the crossing point.