The exploration of model systems exhibiting geometrical spin frustration remains a key avenue for uncovering emergent quantum phenomena. In this work, we report the synthesis and characterization of a different type of frustrated quantum magnets, $\mathrm{Li}A{\mathrm{Nd}}_2{\left({\mathrm{BO}}_3\right)}_3$ $(A=\mathrm{Ba},\mathrm{Sr})$, featuring spatially confined magnetic spin clusters. These compounds host a two-dimensional triangular network of ${\mathrm{Nd}}_6$ spin hexamers in $ab$ planes, separated along the $c$ axis by nonmagnetic $A{\mathrm{O}}_{10}$ and ${\mathrm{BO}}_3$ units. Magnetic susceptibility and specific-heat measurements reveal the realization of an effective $J_{\mathrm{eff}}=1/2$ ground state and the absence of long-range magnetic order or spin freezing down to at least 0.1 K, below which a substantial fraction of spin entropy persists. Under quasi-adiabatic demagnetization from an initial temperature of about 2 K, they exhibit a promising cooling effect, with the temperature-field profile $T\left({\mu }_{0}H\right)$ displaying a distinct minimum or shoulder near 1 T, presumably associated with the intracluster spin correlations. Upon further reducing the field to zero, additional temperature drops down to $\sim 106/117$ mK become evident, hinting at the development of intercluster spin interactions. The probable hierarchical spin interactions and the strong $T\left({\mu }_{0}H\right)$ responses characteristic of both compounds suggest that $\mathrm{Li}A{\mathrm{Nd}}_2{\left({\mathrm{BO}}_3\right)}_3$ is a promising spin-cluster system for exploring quantum spin magnetism and sub-Kelvin magnetocaloric effect.

The ratio of magnetic field penetration length $\lambda$ and superconducting coherence length $\xi$ is a defining quantity that governs magnetic response and underpins the conventional type-I and type-II classification of superconductors. While multicomponent superconductors are known to exhibit multiple coherence lengths with rich and often exotic behavior, single-component superconductors are traditionally assumed to be fully characterized by a single Ginzburg-Landau parameter. Here we revisit this concept. We demonstrate that even nominally single-component superconductors are, in general, intrinsically characterized by multiple coherence lengths. Specifically, we analyze a common physical situation in which a subdominant pairing channel is fully suppressed in the ground state, yielding a nominally single-component superconducting ground state. We show that, nonetheless, proximity to a competing pairing instability generically gives rise to multiple correlation lengths with a nontrivial hierarchy. This has consequences for all inhomogeneous states. Especially near a competing pairing instability, the magnetic field penetration depth lies between two distinct coherence lengths, leading to a breakdown of the conventional type-I and type-II dichotomy and enabling the coexistence of vortex clusters and Meissner domains. More broadly, we find that superconducting states cannot, in general, be classified by a single fundamental length scale, even in ostensibly conventional single-component systems.

We give a recursion relation for the second-quantized fermionic (bosonic) Halperin state, which avoids exact diagonalization of its two-component first-quantized parent Hamiltonian. We validate this formula by proving that the second-quantized Halperin state, as recursively defined in this formula, is indeed a zero mode of the corresponding second-quantized parent Hamiltonian and that it has the correct filling factor.

All-dielectric optical metasurfaces that supporting optical quasibound states in the continuum (QBICs) offer a promising platform in realization of strong light-matter coupling with monolayer transition-metal dichalcogenides (TMDCs). Such coupled systems are critical for wide range of applications in low-dimensional polaritonic physics, optoelectronic and valleytronic devices. Here, we propose a strongly coupled system between Brillouin zone folding driven quasibound states in the continuum (BZF-QBIC) mode of high-index GaP metasurfaces and excitons of monolayer $\mathrm{W}{\mathrm{S}}_2$. By changing the height of the GaP metasurface, we observe a typical anticrossing behavior with a Rabi splitting of 38.2 meV. Simulations also show that the coupling strength is strongly dependent on both the localized electric field enhancement of the metasurface and the linewidth of the BZF-QBIC mode, there is a balance between these two factors for maximizing the coupling effect. Unlike the existing QBIC mode whose resonant wavelength is sensitive to the asymmetric parameter of the dielectric metasurface, BZF-QBICs mode exhibits an asymmetric perturbation-near-independent resonant behavior simultaneously with a high-quality factor, making it ideal for achieving strong coupling in monolayer TMDCs. This work provides a strategy for realizing monolayer TMDCs-assisted strong coupling, and facilitates potential applications in low-dimensional polaritonic devices.

Chiral topological superconductors (TSCs) are conventionally characterized by the bulk Chern number, which dictates the number of chiral Majorana modes at the boundary. However, this single invariant often obscures the rich momentum-space structure of the superconducting gap. In this work, we unveil a hidden topological structure in chiral TSCs by resolving the bulk topology at distinct, high-symmetry points in the Brillouin zone. We demonstrate that TSC phases sharing the same Chern number can be topologically different, distinguished by the distribution of Skyrmions at different high-symmetry points in momentum space. Crucially, the interplay between these invariants and particle-hole symmetry gives rise to anomalous helical Majorana edge modes at the boundaries of TSCs, a phenomenon that is forbidden in the standard Chern-number paradigm. By constructing heterostructures between quantum anomalous Hall insulators (QAHIs) and these refined TSC phases, we utilize nonequilibrium Green's functions and the Landauer–Büttiker formalism to identify unique signatures in thermal conductance. Our findings not only resolve the topological ambiguity in conventional TSC classification but also provide a novel pathway to engineer and manipulate robust Majorana modes, offering new degrees of freedom for topological quantum-computing architectures.

This study investigates the higher-order topological superconductivity (HOTS) in periodically driven ferromagnet–two-dimensional electron gas–superconductor heterostructures with three unconventional pairing symmetries [$s_{\pm }$-, $\left(p_x+i{p}_y\right)$-, and $\left(s+id\right)$-wave ones], which demonstrates that in-plane magnetic field driving universally induces anomalous HOTS across all pairing symmetries. Majorana corner modes exhibit field-strength-dependent spatial localization, four-corner modes for the $s_{\pm }$-wave pairings and two-corner modes for the ($p_x+i{p}_y$)-, and ($s+id$)-wave ones. Most significantly, two distinct orientation-dependent phase transitions are unveiled. One is the transition from an intermediate state (featuring the coexistence of corner and helical edge modes) to a higher-order topological phase (two-corner modes) for the $s_{\pm }$-wave pairings; the other is the alternation between two distinct higher-order phases with different two-corner mode configurations and intermediate states for the $\left(p_x+i{p}_y\right)$-, and $\left(s+id\right)$-wave ones. The findings establish Floquet-driven unconventional pairing superconductor heterostructures as a versatile platform for controlling non-Abelian quasiparticles, opening avenues for designing topologically protected quantum devices through dynamical field manipulation.

Spin-charge stripes are among the most prominent competing orders in high-temperature superconductors. However, this phase is particularly challenging to study numerically due to finite-size effects. Here, we study the formation of long isolated stripes in the $t\text{−}{t}^{\prime }\text{−}J$ model using density-matrix renormalization group simulations on an unusually wide cylindrical strip geometry. This approach allows us to probe the physics of a single stripe largely free from stripe-stripe interactions and commensurability effects. We find that the wide range of stripe filling fractions reported in previous numerical studies is well explained by the physics of an individual stripe. Taking a microscopic look at stripe formation, we reveal two separate regimes—a high-filling regime captured by a simplified squeezed-space model and a low-filling regime characterized by the real-space structure of individual pairs of dopants. Our results connect the phenomenology of stripe order to its microscopic constituents and provide a unified perspective that highlights the different challenges for observing the two regimes in quantum simulation experiments.

Optical orientation of electron and hole spins by circularly polarized light is investigated for ${\mathrm{MAPbI}}_3$ single crystals. The Hanle and polarization recovery effects measured in transverse and longitudinal magnetic fields, respectively, evidence the hyperfine interaction with nuclear spins as the main factor determining the spin dynamics of charge carriers at cryogenic temperatures. The parameters of the nuclear spin fluctuations within the carrier localization volume are evaluated. Dynamic polarization of the nuclear spins is demonstrated by the Overhauser field reaching 5 mT for acting on the electrons and $-30\mathrm{mT}$ for acting on the holes.

Valley splitting in strained Si/SiGe quantum wells is a central parameter for silicon spin qubits and is commonly described with envelope function and effective mass theories. These models provide a computationally efficient continuum description and agree well with atomistic approaches when the confinement potential varies smoothly on the lattice scale. In modern Si/SiGe heterostructures with atomically sharp interfaces and engineered Ge concentration profiles, however, the slowly varying potential approximation underlying conventional (local) envelope function theory is challenged. We formulate an exact multivalley envelope function model by combining Burt–Foreman-type envelope function theory, which does not rely on the assumption of a slowly varying potential, with a valley-sector decomposition of the Brillouin zone. This construction enforces band-limited envelopes, which satisfy a set of coupled integro-differential equations with a nonlocal potential energy operator. Using degenerate perturbation theory, we derive the intervalley coupling matrix element within this nonlocal model and prove that it is strictly invariant under global shifts of the confinement potential (choice of reference energy). We then show that the conventional local envelope model generically violates this invariance due to spectral leakage between valley sectors, leading to an unphysical energy-reference dependence of the intervalley coupling. The resulting ambiguity is quantified by numerical simulations of various engineered Si/SiGe heterostructures. Finally, we propose a simple spectrally filtered local approximation that restores energy-reference invariance exactly and provides a good approximation to the exact nonlocal theory.

We show that proximity to an altermagnet provides an efficient route to engineering non-Hermitian higher-order topological phases. The proximity-induced altermagnetic order gaps the edge states of a topological insulator, thereby driving a transition from a first-order to a second-order topological phase. When combined with nonreciprocal hopping, the system exhibits both the non-Hermitian skin effect and a hybrid skin-topological effect, whereby first-order edge states and second-order corner states accumulate at selected corners of the lattice. We demonstrate that the spectral winding number of the edge states under cylindrical geometry dictates this corner localization and can be reversed by tuning the altermagnetic order. Consequently, both edge and corner states become directionally controllable. Our results establish altermagnets as a versatile platform for realizing and tuning skin-topological phenomena in non-Hermitian higher-order topological systems.

We theoretically predict the giant and robust Josephson diode effect in quasi-one-dimensional topological Majorana nanowires in the regime with multiple subbands, which is expected to be relevant for the real experiment. In the multiband regime, the Majorana bound states and conventional Andreev bound states naturally coexist, and respectively contribute to the fractional and conventional parts in the Josephson effect, with the former/latter having $4\pi /2\pi$ periodicity. We show that the interplay between the two types of bound modes can produce a robust and giant diode effect in the deep topological phase regime. Notably, we unveil a spin-parity exchange mechanism, occurring only in the multiband regime, which leads to a robust high-efficiency plateau of the giant diode effect. This effect is a nontrivial consequence of the balanced Fermi moment shifts of the multiple subbands in tuning the external magnetic field. Our finding highlights the multiband engineering as a powerful tool to optimize the Josephson diode effect realistically and provides a feasible signature to identify topological phase regime in real superconducting nanowires.

The behavior of the paradigmatic $J_1\text{−}{J}_2$ triangular lattice Heisenberg antiferromagnet in a magnetic field remains unsettled despite decades of study. We map out the phase diagram using three complementary approaches, including self-consistent nonlinear spin-wave theory, density-matrix renormalization group, and variational Monte Carlo. This combined analysis resolves the competition among different field-induced magnetic orders and magnetization plateaus across the classically frustrated parameter range. In particular, there is a finite range in the parameter regime around $J_2/J_1=\frac{1}{8}$ in which (i) upon the application of the external field, the gapless quantum spin liquid acquires a finite density of monopoles, and (ii) by further increasing the field, two plateaus are clearly obtained at $m=\frac{1}{3}$ and $m=\frac{1}{2}$. We discuss the experimental importance of the consecutive magnetization plateau transitions as a signature of an underlying quantum spin-liquid phase.

The transfer of oxide membranes provides a new dimension in material design that goes beyond the limitations of classical hetero-epitaxy. For example, the transfer of freestanding membranes offers the in-plane twist angle between film and substrate as a tuneable degree of freedom. An ideal twist boundary yields formation of an in-plane screw-dislocation network to reduce interfacial stress. Previously, periodic screw-dislocation networks have been demonstrated by wafer bonding of two crystals, where the twist boundary is embedded in the bulk and made accessible to detailed characterization mostly by destructive methods. Recent approaches exploited freestanding membranes to create twist boundaries with the interface located only nanometers beneath the surface, making it readily accessible by near-surface-sensitive techniques. In this work, both approaches were combined to transfer membranes on the mm²-scale via wafer bonding and subsequent release by etching the sacrificial layer. High-resolution synchrotron-based grazing incidence x-ray diffraction was performed to investigate the structure of the twisted ${\mathrm{SrTiO}}_3/{\mathrm{SrTiO}}_3$ interface. In order to gain a better qualitative and quantitative understanding of the experimental results, we simulated the x-ray diffraction of twisted perovskites based on continuum elastic theory and kinematical scattering. Our measurements show that the measured diffraction patterns are consistent with the formation of a periodic screw-dislocation network, since the apparent superlattice reflections coincide with the obtained diffraction pattern from simulations. However, the intensity profile and appearance of specific symmetry-forbidden diffraction peaks in the experiments cannot be described by elastic displacements alone.

Understanding the microscopic origin of intrinsically low lattice thermal conductivity is crucial for the design of thermoelectric materials. Here, the lattice dynamics and thermal transport of layered $X\mathrm{Ag}Y (X=\mathrm{K},\mathrm{Rb},\mathrm{Cs};Y=\mathrm{S},\mathrm{Se},\mathrm{Te})$ compounds with the P4/nmm structure are investigated using first-principles calculations by explicitly accounting for high-order anharmonicity and phonon coherence. All $X\mathrm{Ag}Y$ compounds exhibit remarkably low lattice thermal conductivity, with ${\kappa }_L$ at 300 K confined to a narrow range of approximately 0.334–$0.643\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$, reaching as low as $0.334\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ in CsAgTe. The strong suppression of the incoherent (Peierls-type) contribution originates from pronounced quartic anharmonicity and enhanced four-phonon Umklapp scattering, which can be traced to the distorted Ag–Y tetrahedral environment and the associated nonuniform distribution of bonding rigidity, giving rise to an anomalously strong bond–strong anharmonicity coupling. Beyond the phonon gas model, coherent phonon transport becomes non-negligible at elevated temperatures, particularly along the $c$ axis, arising from strong inter-branch coupling among high-frequency optical phonons that enables wave-assisted energy transfer. These results reveal a cooperative mechanism combining high-order anharmonicity and phonon coherence, providing a transport paradigm beyond the Peierls picture for intrinsically low-${\kappa }_L$ layered materials.

All-$d$ Heusler alloys are promising candidates for advanced spintronic and magnetoelastic applications, yet many lack the intrinsic large anomalous Hall conductivity (AHC) and magnetostriction required for practical device integration. In this work, we systematically investigate the topological transport and magnetostrictive properties of 81 heavy-element substituted Co-based all-$d$ Heusler alloys ${\mathrm{Co}}_{2}YZ\left(R\right)$ $(Y=\mathrm{Cr},\mathrm{Mn},\mathrm{Fe};Z=\mathrm{Sc},\mathrm{Ti},\mathrm{V}; \text{and} R=\mathrm{Re},\mathrm{Os},\mathrm{Ir},\mathrm{Pt})$ using first-principles calculations. We demonstrate that the fractional substitution of $5d$ transition metals serves as a highly effective strategy to tune the electronic structure via strong spin-orbit coupling (SOC). Our calculations identify eight materials exhibiting giant AHC values exceeding 1000 S/cm, with ${\mathrm{Co}}_2{\mathrm{Mn}}_{0.75}{\mathrm{Os}}_{0.25}\mathrm{Sc}$ and ${\mathrm{Co}}_2{\mathrm{Mn}}_{0.75}{\mathrm{Re}}_{0.25}\mathrm{V}$ approaching 1500 S/cm. Detailed symmetry and electronic structure analyses reveal that this massive AHC originates from the SOC-induced gap opening of Weyl nodal lines near the Fermi level, which generates an extended distribution of large Berry curvature. Furthermore, the introduction of strong SOC significantly enhances the magnetocrystalline anisotropy energy, transforming alloys with initially negligible magnetostriction into high-performance magnetoelastic materials. Notably, ${\mathrm{Co}}_2{\mathrm{Fe}}_{0.75}{\mathrm{Os}}_{0.25}\mathrm{Ti}$ and ${\mathrm{Co}}_2{\mathrm{FeSc}}_{0.75}{\mathrm{Ir}}_{0.25}$ exhibit giant magnetostriction coefficients of 752 and 609 ppm, respectively. Our findings establish heavy-element substitution as a robust, dual-purpose approach for the design and realization of multifunctional topological magnetic materials.

The development of room-temperature magnetic semiconductors is critical for advancing spintronic technologies, yet van der Waals magnets like ${\mathrm{CrI}}_3$ exhibit intrinsically low Curie temperatures ($T{}_{\mathrm{C}} \sim 45$ K). This study employs first-principles calculations to demonstrate that atom intercalation, particularly lithium (Li), dramatically enhances magnetic-exchange couplings in ${\mathrm{CrI}}_3$, achieving near-room-temperature ferromagnetism with a predicted $T{}_{\mathrm{C}}$ of 286 K, aligning with experimental reports of 420 K. The underlying mechanism involves synergistic superexchange and double-exchange interactions: intercalation reduces the $|E_p-E_d|$ energy difference between iodine p-orbitals and chromium $d$ orbitals, strengthening superexchange pathways, while charge transfer induces valence mixing (e.g., ${\mathrm{Cr}}^{3+}$ to ${\mathrm{Cr}}^{2+}$, as confirmed by experimental x-ray photoelectron spectrometry data), promoting double exchange. Theoretical predictions extend to other intercalants including Cu and Na, with ${\mathrm{Cu}}_{0.25}{\mathrm{CrI}}_3$ and ${\mathrm{Na}}_{0.25}{\mathrm{CrI}}_3$ exhibiting $T{}_{\mathrm{C}}$ of 267 K and 247 K, respectively, establishing a versatile strategy for designing high-$T{}_{\mathrm{C}}$ magnetic semiconductors. This work bridges theoretical insights and experimental validation, offering a transferable framework for intercalation-driven material design and accelerating practical spintronic device realization.

Lithium-abundant electrides, characterized by the presence of interstitial anionic electrons, have attracted considerable attention owing to their extraordinary properties, including superconductivity. Here, we conduct comprehensive first-principles structure-prediction simulations to investigate the phase stability of lithium-platinum (Li-Pt) compounds under high-pressure conditions. Our calculations identify several hitherto unknown electride phases in the Li-Pt system, namely, $\mathrm{L}{\mathrm{i}}_4\mathrm{Pt}, \mathrm{L}{\mathrm{i}}_5\mathrm{Pt}, {\mathrm{Li}}_6\mathrm{Pt}, {\mathrm{Li}}_{11}\mathrm{Pt}$, and $\mathrm{L}{\mathrm{i}}_{12}\mathrm{Pt}$. Among the metallic phases uncovered, ${\mathrm{Li}}_6\mathrm{Pt}$ exhibits the highest superconducting critical temperature ($T_{\mathrm{c}}$), reaching 18 K at 120 GPa. Strikingly, $\mathrm{L}{\mathrm{i}}_{12}\mathrm{Pt}$, the phase with the highest lithium content, is unexpectedly predicted to be a semiconductor. We further clarify the fundamental criteria governing interstitial electron localization and establish systematic correlations between superconductivity and key electronic and vibrational descriptors, including the electronic density of states, electron-phonon coupling strength, and phonon softening across all predicted phases. These results substantially broaden the structural diversity of the Li-Pt system and underscore the intriguing coexistence of superconductivity and semiconducting behavior in lithium-based electride materials.

Current-induced spin-orbit torques (SOTs) provide a crucial mechanism for the electrical control of antiferromagnetic order. However, SOTs in antiferromagnets (AFMs) and the resulting spin dynamics remain largely unexplored. Here we present a complete classifications of SOTs in bulk collinear AFMs based on magnetic point group symmetry. Depending on the symmetry operations that connect the two antiparallel spin sublattices, the SOTs are categorized into six distinct types. We focus on three representative AFMs in which the spin sublattices are linked by fractional translation, spatial inversion, or neither of these symmetries, respectively. Using first-principles calculations within Kubo linear response theory, we compute the SOTs on each sublattices, and simulate the Néel vector dynamics via the Landau-Lifshitz-Gilbert equation. In the prototypical $\mathit{PT}$-symmetric AFM and the inversion symmetry breaking altermagnet, our simulations reveal that deterministic Néel vector switching can be driven entirely by field-like torques. Moreover, all-electrical writing of a single domain state with preset Néel vector direction, as well as ${180}^{\circ }$ deterministic switching is attainable. This work sheds light on current-controlled antiferromagnetic orders in collinear AFMs. In particular, for the inversion symmetry breaking altermagnet, the demonstrated electrical writing and reading of the Néel vector hold promise for antiferromagnetic memory applications.