The van der Waals (vdW) antiferromagnets with a large uniaxial magnetocrystalline anisotropy (UMA) have compelling advantages for terahertz spintronics applications. Although the temperature dependence of UMA is essential for ensuring device endurance, it has scarcely been explored. Here, we unveil an unconventional temperature dependence of UMA in vdW antiferromagnet ${\mathrm{FePS}}_3$. The easy-magnetization axis exhibits an anomalous transition from in-plane to out-of-plane above 110 K under a low magnetic field, with this behavior persisting even beyond the Néel temperature of 118 K. Temperature-dependent x-ray diffraction measurements combined with density functional theory calculations reveal that the switching originates from an anomalous transition from an antiferromagnetic to a quasiferromagnetic state. This transition is governed by the evolving competition between significantly strengthened intra-subchain ferromagnetic coupling and drastically diminished inter-subchain antiferromagnetic coupling upon heating; thereby, the latter becomes ultimately suppressed as a consequence of substantial lattice thermal expansion and the intrinsic antiparallel zigzag configuration of the ferromagnetic subchains. Our findings offer not only the basic understanding of the temperature dependence of UMA in vdW antiferromagnetic materials but also the low magnetic field- and temperature-tunable magnetic states by considering the cooperation between lattice and antiferromagnetic exchange coupling for terahertz spintronics applications.

Owing to a power-law anisotropy in the quasiparticle dispersion, yielding an enhanced density of states, the effects of long-range Coulomb interaction get amplified in three-dimensional generalized Weyl semimetals, characterized by integer monopole charge $n>1$ of the underlying Weyl nodes. Using a Wilsonian renormalization group approach controlled by a large-$N$ expansion with $N$ as the number of Weyl fermion flavors and a gauge-consistent regularization fixed by the Ward-Takahashi identity, we uncover for $n\ge 2$ an extended interaction-dominated scaling regime with intrinsically anisotropic dynamic Coulomb screening, a finite fermionic anomalous dimension, and a power-law suppression of the quasiparticle residue, yielding an anisotropic marginal non-Fermi liquid at intermediate energies. Ultimately, the effective fine structure constant flows to zero, albeit only logarithmically slowly, so the marginal Fermi liquid phenomenology emerges as a broad crossover, controlled by a slowly running coupling. By contrast, for $n=1$ the system retains an isotropic marginal Weyl-liquid character. These predictions can be tested via scaling in thermodynamics (specific heat and compressibility), direction-dependent optical conductivity, and by anisotropic broadening of the single-particle spectral function in angle-resolved photoemission spectroscopy.

Controlling magnons in magnetic insulators is key to their application in spintronics. In this work, we study the magnon spin photocurrent in effective spin models for ${\mathrm{Cr}}_2{\mathrm{O}}_3$, a material known for its magnetoelectric (ME) effect. Using the nonlinear response theory, we show that the magnon spin current can be generated by both linearly and circularly polarized electromagnetic waves via one-magnon processes. For linearly polarized waves, the spin current arises even in the absence of a static magnetic field. In contrast, circularly polarized waves induce a spin current only when a static magnetic field is present, and the current reverses its direction upon inversion of the field. The sensitivity to the external magnetic field and the contrasting behaviors under linearly and circularly polarized electromagnetic waves delineate the spin photocurrent from other competing contributions, such as spin pumping and inhomogeneous heating, facilitating experimental verification. Our results show that ${\mathrm{Cr}}_2{\mathrm{O}}_3$ is an interesting candidate for the experimental investigation of the magnon photocurrent.

We present a comprehensive study of the temperature- and magnetic-field-dependent magnetization, specific heat, and local crystal structure across the first-order ferromagnetic–paramagnetic transition in ${\mathrm{Eu}}_2\mathrm{In}$. Anomalies in the magnetocaloric response are observed near $H\approx 25$ kOe, including changes in field scaling of magnetic entropy, local entropy exponent, and universal master curve, which suggest an apparent weakening of the first-order character of the transition. However, quantitative analysis of the magnetocaloric parameters together with modified Arrott plots demonstrates that the transition remains first order up to at least 70 kOe. Specific-heat measurements reveal a field-induced splitting of the sharp zero-field anomaly into a doublet, providing a natural explanation for the change in the magnetocaloric response. Magnetic-field-dependent extended x-ray absorption fine structure (EXAFS) measurements show no detectable field-induced changes in the local coordination environment of Eu. We therefore attribute these observations to a magnetic-field-induced two-step transition process in ${\mathrm{Eu}}_2\mathrm{In}$.

Rare-earth triangular lattices provide an ideal platform for exploring novel quantum magnetic states. Here, we report the crystal growth and magnetic properties of a rare-earth triangular-lattice compound, ${\mathrm{ErZn}}_3{\mathrm{P}}_3$. Alternating-current magnetic susceptibility and specific heat measurements reveal a long-range antiferromagnetic order below $T=0.12\mathrm{K}$. The long-range magnetic order can be rapidly suppressed by a small magnetic field of ${\mu }_{0}H=0.04\mathrm{T}$ along the $c$ axis, followed by a broad field-induced anomaly above 0.05 T that shifts to higher temperatures as the magnetic field increases. The magnetic entropy release below 2 K is estimated to be $0.852\left(42\right)Rln2$, which is consistent with a Kramers doublet described by an effective spin $S=1/2$. Finally, a magnetic field-temperature contour map is constructed based on the specific heat results. Our work identifies a long-range yet fragile magnetic order in this newly grown $S=1/2$ quantum magnet, and its fragility suggests the presence of strong quantum fluctuations arising from geometric frustrations and quantum spins in ${\mathrm{ErZn}}_3{\mathrm{P}}_3$.

The determination of how the phase of the superconducting order parameter in a superconductor varies with the spatial direction, which can be done only through Josephson-effect-based phase-sensitive measurements, is crucial for the establishment of the precise pairing symmetry of the superconductor. So far, such measurements have been done on high-$T_c$ cuprate superconductors but only in a couple of directions for $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$ because of the difficulty in preparing Josephson junctions between $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$ and an $s$-wave superconductor with a chosen mutual orientation. Another long-standing issue in $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$, which was shown previously to feature a spontaneously broken time-reversal symmetry by muon spin rotation and other measurements, is that the expected presence of chiral surface currents, domains, and domain walls is yet to be explicitly shown experimentally. To address these issues, we have long sought the preparation of high-quality Josephson junctions between $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$ and a conventional $s$-wave with a controllable orientation relative to the symmetry axes in $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$. We report in this article the successful fabrication of ramp Josephson junctions of Al/Ti/$\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$ on thin single crystals of $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$ obtained by mechanical exfoliation. These junctions were found to show high-quality quantum oscillations consistent with a single-domain Josephson coupling. The normal junction resistance was found to depend extremely sensitively on the supercurrent flowing in the $\mathrm{S}{\mathrm{r}}_2\mathrm{Ru}{\mathrm{O}}_4$ crystal on which the Josephson junction was made. This finding was used in the present work to provide an estimate of the size of the chiral surface current, which is shown to agree with its upper bound established previously.

Spin-triplet superconductors are promising platforms for dissipationless spin transport, which typically originates from the interplay of ferromagnetism and superconductivity. However, ferromagnetism, in turn, suppresses superconductivity. As a class of unconventional magnetic materials, $p$-wave magnets possess the advantage of odd-parity spin splitting without net magnetism. Here we demonstrate through site-resolved spin-polarized band analysis that $p$-wave magnets exhibit nonzero in-plane spin polarization, which is crucial for spin-triplet correlations. We then investigate the $p$-wave magnetic superconductor composed of a $p$-wave $\mathrm{magnet}/s$-wave superconductor hybrid system and calculate the site-resolved equal-spin component of anomalous Green's function, revealing the existence of equal-spin (spin-triplet) Cooper pairs. Next, we construct a normal $\mathrm{metal}/p$-wave magnetic superconductor junction and calculate the equal-spin Andreev reflection coefficient using the nonequilibrium Green's function method. The results show that the equal-spin Andreev reflection coefficient is indeed nonzero, owing to the spin-triplet superconductivity. Finally, we construct a Josephson junction based on $p$-wave magnetic superconductors, study the spin Josephson effect, and identify the emergence of a spin superconducting diode effect.

Recent theories have predicted the existence of another class of hafnium superhydride $P{6}_3/mmc\text{−}\mathrm{Hf}{\mathrm{H}}_{10}$ with a two-dimensional layered structure and remarkable high-$T_{\mathrm{c}}$ around 213–234 K at 250 GPa. Its structure contains a planar pentagraphenelike hydrogen sublattice, which does not resemble the discovered high-$T_{\mathrm{c}}$ superconductors of covalent-bonded hydrogen structure of ${\mathrm{H}}_3\mathrm{S}$ and clathrate-type structure of $\mathrm{La}{\mathrm{H}}_{10}$. Here, we present the synthesis of hafnium superhydrides by the direct chemical reaction of Hf and ${\mathrm{H}}_2$ or with ammonia borane as the hydrogen source in laser-heated diamond anvil cells ranging from 200 to 302 GPa. Synchrotron x-ray diffraction data reveal the presence of previously predicted $\mathit{Pm}\overline{3}n\text{−}\mathrm{Hf}{\mathrm{H}}_3$, Fddd-$\mathrm{Hf}{\mathrm{H}}_4$, and $C2$/m-$\mathrm{Hf}{\mathrm{H}}_{14}$ phases, and a unique triclinic phase $P\overline{1}\text{−}\mathrm{Hf}{\mathrm{H}}_{10.5}$ was identified. Unfortunately, no existence of the $P{6}_3/mmc\text{−}\mathrm{Hf}{\mathrm{H}}_{10}$ phase was detected in the studied pressure range. Electrical resistance measurements demonstrate the synthesized products exhibiting good metallic character and absence of superconductivity down to $\sim 80$ K. Theoretical calculations reveal the presence of the atomic H and ${\mathrm{H}}_2$ molecular units within the structure of $P\overline{1}\text{−}\mathrm{Hf}{\mathrm{H}}_{10.5}$, which is mainly responsible for the low superconducting temperature.

In correlated electronic states, observation of size-dependent nucleation and melting is rarely reported, likely due to the extremely small length scales necessary to observe such effects for electronic states. Here, using $1T\text{−}\mathrm{Ti}{\mathrm{Se}}_2$ nanoflakes as a prototypical two-dimensional charge density wave (CDW) system, we perform in situ cryogenic electron microscopy with temperature down to 20 K and observe size-dependent melting of CDWs. Specifically, we observe a melting point depression of CDW for $1T\text{−}\mathrm{Ti}{\mathrm{Se}}_2$ flakes with lateral sizes less than 100 nm. By fitting experimental data to a Ginzburg-Landau model, we estimate a zero-temperature correlation length of 10–50 nm, which matches the reported CDW domain size for $1T\text{−}\mathrm{Ti}{\mathrm{Se}}_2$. As the flake size approaches the correlation length, the divergence of the CDW correlation length near the transition is cut off by the finite flake size, limiting long-range order and thereby lowering the transition temperature. For very small flakes whose size is close to the correlation length, we also observe absence of long-range CDW, as predicted by the model.

The creation of high-quality cluster states in superconducting microwave circuits is a relevant ingredient in continuous-variable quantum computing. Although large-scale cluster states have been established in optical systems, dissipation prevents their direct applicability to the microwave realm. Recent improvements in superconducting parametric circuits, in particular Josephson parametric amplifiers (JPA) and traveling wave parametric amplifiers (TWPA), have permitted substantial progress in producing entangled states using microwave photons. In this paper, we examine experimentally and theoretically the effects of numerous parametric pump tones on the degree of two-mode squeezing in a quantum circuit and apply it to the JPA. We find that additional pumps diminish the initial two-mode correlations achieved with a single pump by redistributing it among a larger network of modes and by introducing entanglement with additional idler frequencies. Taking into account the actual heterodyne measurement conditions, the experimental results are consistent with theoretical expectations.

Hole degrees of freedom play a central role in the exact solution of quadratic (mean-field) systems. Although a variety of experiments have suggested the existence of bosonic holes, a consistent and complete theory has long been hindered by the ghost problems. Here, we resolve the ghost problem and establish a unified theoretical framework for bosonic holes by introducing the $\mathcal{CPT}$ theory and bosonic particle-hole (PH) transformation. The bosonic analogs of the ‘‘Fermi surface’’ and ‘‘Fermi level’’ are proposed. Furthermore, PH duality between Hermitian and non-Hermitian quadratic bosonic systems (QBSs) is revealed. In both distinct QBSs, the $\mathcal{C}$ parity is shown to label PH-conjugate eigenspaces. Building on this duality, we demonstrate PH Bogoliubov quasiparticles in $\mathcal{APT}$ symmetric Hamiltonians, investigate the dynamical generation of PH entanglement, and predict Hermitian PH Aharonov-Bohm interference in non-Hermitian QBSs.

Artificial spin ice (ASI) systems exhibit fascinating phenomena, such as frustration and the formation of magnetic monopole states, and Dirac strings. However, exploring the wave phenomena in these systems is elusive due to the weak dipolar coupling that governs their interactions. In this study, we demonstrate coherent spin-wave propagation in a hybrid ASI system, which is based on a multilayered ferromagnetic thin film with perpendicular magnetic anisotropy and in-plane magnetized nanoelements immersed within it. We show that this system enables spin-wave transmission over a one-micrometer distance via exchange-mediated coupling between subsystems and evanescent spin-wave tunneling through the out-of-plane magnetized parts. This system overcomes the limitations of purely dipolar interactions in standard ASIs while preserving their fundamental properties. Thus, it provides a platform for studying spin-wave phenomena in frustrated ASI systems and paves the way for exploiting them in analog signal processing with spin waves.

Machine learning and high-throughput screening approaches to superconductor discovery require physically meaningful descriptors that capture essential physics while remaining computationally tractable. The superfluid weight is an ideal descriptor as it is a prerequisite for superconductivity, determines the magnetic penetration depth and the Berezinskii-Kosterlitz-Thouless transition temperature in two-dimensional materials, may limit the critical temperature in unconventional superconductors through phase coherence, and reveals quantum geometric contributions to supercurrent transport. We develop a computationally efficient framework for calculating the zero-temperature, mean-field superfluid weight for uniform pairing from density functional theory band structures and Bloch wave functions. We separately evaluate the conventional contribution from band curvature and the geometric contribution from quantum geometry. To validate the method, we calculate London penetration depths for a few conventional superconductors (Al, Pb, Nb, ${\mathrm{MgB}}_2, {\mathrm{LuRu}}_3{\mathrm{B}}_2$, and ${\mathrm{YRu}}_3{\mathrm{B}}_2$) and find good agreement with experiment after accounting for nonlocal corrections, strong-coupling effects, and sample quality. The conventional contribution dominates by orders of magnitude in these wideband materials, as expected. This framework provides a foundation for large-scale screening of superconducting candidates and exploring quantum geometric effects in unconventional superconductors.

Twisted bilayer graphene aligned with hexagonal boron nitride (TBG/hBN) hosts rich topological and correlated quantum phases, such as (fractional) Chern insulators, whose character is dictated by the topology of the moiré flat band. This topology is highly sensitive to several material parameters in the continuum model, yet a systematic understanding of their combined influence has been lacking. Here, we present a comprehensive study of topological phase transitions in TBG/hBN by varying the interlayer hopping strengths ($w_0,w_1$) and hBN-induced staggered potential, both with and without the hBN moiré potential. We map out Chern number phase diagrams across a broad, experimentally relevant parameter space, revealing a progressive enrichment of the topological landscape including multiple high-Chern-number ($C$ = 3, 4, and 5) states. Each transition is linked to distinct band-inversion mechanisms at generic $C_3$-symmetric $k$ points, high-symmetry momenta, or parabolic touchings, clearly reflecting in the evolution of the Berry curvature. Our results offer theoretical insights that help interpret existing experimental observations, elucidate the mechanisms driving these topological phase transitions, and facilitate the exploration of topological states in TBG/hBN and related moiré systems.

Flat bands (FBs) with compact localized eigenstates (CLSs) fall into three main categories, controlled by the algebraic properties of the CLS set: orthogonal, linearly independent, and linearly dependent (singular). A CLS parametrization allows us to continuously tune a linearly independent FB into a limiting orthogonal or a linearly dependent (singular) one. We derive the asymptotic real-space decay of the flat-band projectors for each category. The linearly independent FB is characterized by an exponentially decaying projector and a corresponding localization length $\xi$, both dressed by an algebraic prefactor. In the orthogonal limit, the localization length is $\xi =0$, and the projector is compact. The singular FB limit corresponds to $\xi \to \infty$ with an emerging power-law decay of the projector. Furthermore, we identify an anisotropic singular flat-band class with direction-dependent band touchings, which exhibits anisotropic algebraic decay of the flat-band projector. This anisotropy is unavoidable in three-dimensional two-band lattices with real CLSs. We obtain analytical estimates for the localization length and the algebraic power-law exponents depending on the dimension of the lattice and the number of bands involved. Numerical results are in excellent agreement with the analytics. Our results are of relevance for the understanding of the details of the FB quantum metric discussed in the context of FB superconductivity, the impact of disorder, and the response to local driving.

The interplay between band and atomic aspects in materials with coexisting wide-band and flat-band states, or wide-band and effectively dispersionless electronic states is increasingly expected to lead to novel behavior. Using dynamical mean-field theory (DMFT), we investigate strange metal-like behavior and emergence of unconventional superconductivity in a toy model that captures this interplay. Surprisingly, we find good accord with transport features seen in underdoped cuprates and ladder Fe arsenides. We connect our findings to proposals of ${\mathrm{FL}}^{*}$ and orthogonal Fermi liquids, and present a route to its direct instability to novel, competing orders.

The electronic structure of ${\mathrm{VSe}}_2$ with $4\times 4\times 3.18$ charge density wave (CDW) transition has been studied by means of angle-resolved photoemission spectroscopy (ARPES) and scanning photoemission microscopy (SPEM). The partial depletion of the Fermi surfaces is observed in the CDW phase by ARPES, consistent with that reported previously. A flat band with V $3d3z^2\text{−}{r}^2$ character, which is observed near the Fermi level around the $\mathrm{\Gamma }$ point in the Brillouin zone, gains its spectral weight in the CDW phase while the holelike band around the $A$ point loses its weight. The spectral weight redistribution across the CDW transition indicates an important role of the V $3d$-Se $4p$ hybridization, associated with the out-of-plane displacement of Se reported by Petkov et al. [Phys. Rev. B 111, 014105 (2025)]. The electronic inhomogeneity observed by SPEM suggests different surface terminations of the CDW state with the strong lattice and electronic modulation along the out-of-plane direction.

Twisted bilayer graphene (TBG) is known to have disorder in its twist angle. We show that in terms of a Dirac equation with a random gauge potential $\mathbf{A}\left(\mathbf{r}\right)$, this disorder becomes huge when the average twist angle is near the magic angle where the Dirac velocity vanishes. The density of states then diverges at the Dirac point as $\rho \left(E\right)\sim E^{(2/z)-1}$ with $z\gg 1$, and we deduce that electrons occupy energies very near $E=0$. We solve a strong disorder problem by deriving a sum rule on the disorder averaged eigenfunctions from which we deduce that each added electron contributes equal intraband Coulomb interaction energy. The various bands in TBG are related by either $\mathbf{A}\left(\mathbf{r}\right)\to \mathbf{A}(-\mathbf{r})$ or $\mathbf{A}\left(\mathbf{r}\right)\to -\mathbf{A}\left(\mathbf{r}\right)$, which affects the interband interaction energy. We find, within Hartree-Fock, jumps in the chemical potential at each integer filling, accounting for the cascade transitions.

The photonic spin Hall effect (PSHE), a typical manifestation of spin-orbit interactions of light, is characterized by a transverse shift δ of photons with opposite spins. Precise measurement of this shift advances spin-dependent technologies, including precision metrology and optical sensing. Previous schemes to enhance the typically small shifts ($\delta /\lambda <{10}^{-1}$, where $\lambda$ is the operation wavelength) are limited to narrow angular cones ($\mathrm{\Delta }\theta <1^{\circ }$). While some efforts have achieved a giant PSHE over either broad bands or wide angles, combining both advantages cannot realize. Here, we demonstrate an enhanced PSHE (δ/$\lambda >0.5$) simultaneously over a broad midinfrared band ($13\sim 20\mu \mathrm{m}$) and a wide angular width ($\mathrm{\Delta }\theta =21.7^{\circ }$) using doped indium arsenide (InAs) multilayer films with gradient epsilon-near-zero (ENZ). Though applying a moderate magnetic field, the ENZ property and material loss of the anisotropic InAs films excite leaky $p$-polarized electromagnetic modes under $p$ polarization waves incident, leading to high broadband absorption. This absorption significantly outweighs that of $s$ polarization waves (which lack leaky modes), causing strong polarization splitting. Notably, this splitting is insensitive to incident angle and layer thickness variations, yielding a highly robust, wide-angle PSHE. This mechanism can be generalized to other III-V semiconductors, magnetized metals, topological Weyl semimetals, and zero refractive index metasurfaces.