We report a comprehensive study of spin-$\frac{1}{2}$ quantum magnet brochantite, ${\mathrm{Cu}}_4{\mathrm{SO}}_4{\left(\mathrm{OH}\right)}_6$, combining high-field thermodynamic measurements, polarized neutron diffraction, inelastic neutron scattering, and nuclear magnetic resonance spectroscopy. Using bulk magnetization and specific heat measurements we construct the magnetic $H\text{−}T$ phase diagram for magnetic fields applied along main crystallographic directions up to 24.1 T. Polarized neutron diffraction reveals a noncollinear magnetic ground state confined to the $ab$ plane. A field-induced transition is observed for magnetic fields in the $ab$ plane whose critical field and character evolve continuously with field direction in the $ab$ plane. While the transition for $H\parallel b$ might be a spin-flop-like transition, the one for $H\parallel a$ resembles the short-range correlated state above $T_{\mathrm{N}}$, suggesting a magnetic configuration related to the quasi-two-dimensional correlations in the $bc$ planes. The experimental results demonstrate that the ground-state and field-induced phases cannot be explained by a simple XXZ model with a single dominant exchange interaction and that weaker interchain and anisotropic interactions have to be taken into account. Our work establishes brochantite as a low-symmetry Cu-based quantum magnet with noncollinear order and complex field-induced behavior.

A combined experimental and first-principles investigation of the magnetic hyperfine field at dilute Ce impurities in the antiferromagnetic intermetallics ${\mathrm{GdIn}}_3$ and ${\mathrm{TbIn}}_3$ is reported here. Perturbed angular correlation spectroscopy using ${}^{140}\mathrm{Ce}$ probes reveals strongly reduced hyperfine fields of $\sim 13\mathrm{T}$ in both hosts, which are substantially smaller than the free-ion value and even reduced relative to ${\mathrm{CeIn}}_3$. To elucidate the local origin of this suppression, we perform spin-polarized density functional calculations including spin-orbit coupling within supercell models that explicitly account for the antiferromagnetic order. A systematic comparison of local spin-density approximation (LSDA), $\mathrm{LSDA}+U$, and hybrid B3PW91 functionals demonstrates that the hyperfine field at the Ce site is overwhelmingly dominated by the orbital contribution associated with the $4f$ shell, while spin-dipolar and Fermi-contact terms nearly cancel out. Conventional $\mathrm{DFT}+U$ (DFT being density functional approximation) artificially localizes the Ce $4f$ states and strongly overestimates hyperfine field. In contrast, calculations with a hybrid functional with enhanced exact exchange reveal a resonance-like $4f$ spectral weight at the Fermi level, yielding nearly quenched spin moments and hyperfine fields in excellent agreement with the experiment. Analysis of the electronic structure and charge-density redistribution indicates that the reduced lattice volume (from lanthanide contraction) of the ${\mathrm{GdIn}}_3$ and ${\mathrm{TbIn}}_3$ hosts exerts an effective chemical pressure on the Ce impurity comparable to the critical pressure of ${\mathrm{CeIn}}_3$, thereby driving the Ce $4f$ electrons into an intermediate-valence regime. These results establish hyperfine interactions as a sensitive microscopic probe of $4f$ hybridization and demonstrate the importance of beyond-semilocal exchange-correlation functionals for reliable predictions of hyperfine properties in correlated rare-earth materials.

We study how topological crystalline defects—dislocations—reshape the real-space quantum geometric tensor and act as tunable sources of quantum geometry. We show that dislocations strongly enhance the quantum metric, establishing a direct link between lattice topology and the Hilbert-space geometry of states. We characterize the quantum geometry of topological magnons in ordered arrays of dislocations, demonstrating that defect-induced geometric enhancement controls their localization and topological protection. In disordered arrays, dislocation-driven geometry expands the accessible topological phase space and enables transitions to disorder-induced topological phases. Our results identify the quantum metric as a tunable bridge between crystalline topology, magnonic excitations, and emergent topological matter in aperiodic solid-state and synthetic systems.

The magnetic nature of the altermagnet candidate ${\mathrm{RuO}}_2$ remains under debate. It has been recently shown from quantum oscillations and angle-resolved photoemission spectroscopy that the high-quality ${\mathrm{RuO}}_2$ bulk single crystal is a paramagnetic metal. Here we report the specific heat and magnetic susceptibility in ultraclean ${\mathrm{RuO}}_2$ single crystals with residual resistivity ratio up to 1200. The electronic specific heat, the magnetic susceptibility, and the $T^2$ coefficient in resistivity point to a weakly correlated three-dimensional Fermi-liquid state, as supported by the Wilson and Kadowaki-Woods ratios. The magnetic susceptibility increases with temperature and is phenomenologically fitted with an inclusion of $T\text{ln}(T/T_0)$ over a wide temperature range up to 400 K. In contrast, the energy dependence of the density of states and thermal activation of quasiparticles lead to a decrease with temperature. Such characteristic temperature dependence, similar to that observed in other $d$-electron metals, is attributable to an enhanced orbital contribution arising from lattice-expansion-induced changes in the band structure.

Here we argue that the angular harmonics of magnetotransport directly characterizes carrier imbalances in a multiband semimetal. A robust threefold modulation superimposed on the conventional $cos\theta$ angular Hall response is observed in ${\mathrm{WTe}}_2$ in the metallic regime at low temperatures under out-of-plane magnetic-field rotation. By tuning temperature and thickness, we demonstrate that this modulation is intrinsic and originates from enhanced nonlinear Hall response arising from its near-compensated two-band electronic structure. In contrast, a few-layer graphene exhibits a richer hierarchy of higher-order angular harmonics, consistent with its multiple dynamically distinct bands. By carefully ruling out extrinsic artefacts and employing Fourier analysis, we establish angular harmonic analysis as a sensitive probe of electronic structure in multiband semimetals.

Spin qubits are a promising platform for quantum computation and can operate at temperatures ranging from tens of millikelvin to a few kelvin. Some recent experiments have revealed a nontrivial, often nonmonotonic dependence of the qubit frequency on temperature, including regions of reduced temperature sensitivity. Motivated by these observations, we investigate whether the interaction of a spin qubit with phonons of the host material can contribute to such frequency shifts in the low-temperature regime. While the resulting shifts are too small to quantitatively account for the experimentally observed magnitudes, our analysis reproduces several qualitative features, including nonmonotonic temperature dependencies and sign changes of the frequency shift. More generally, we demonstrate that phonons can induce a temperature-dependent renormalization of the qubit frequency and provide insight into the interaction between spin qubits and their host material. Understanding and quantifying such individual contributions is an important step toward identifying the microscopic mechanisms underlying the experimentally observed temperature dependence of spin-qubit frequencies.

Skyrmions are topologically protected solitons with great potential as information carriers. Initially explored in condensed-matter physics, they have recently garnered much attention in photonics. Photonic skyrmions constructed from magnetic field vectors in electromagnetic waves are typically localized, long-range propagating skyrmions. They possess both theoretical and practical significance but remain elusive. Here, we report a class of high-fidelity optical counterparts capable of propagating over long distances in tubular structures, which satisfy the exact wave solutions of Maxwell's equations. By leveraging transformation optics to connect the material parameters with the vector field, the intrinsically twisted skyrmions with customized helicity are predicted in an anisotropic waveguide, where the required material parameters can be realized through effective medium theory. These propagating skyrmions with abundant helicity provide additional degrees of freedom to manipulate electromagnetic waves across space and time, further paving the way for applications in chiral sensing, information transmission, and storage.

We show that magnetism in moiré Mott-Wigner crystals can be induced by the collective vibration of electrons around their equilibrium positions (namely, electronic phonons), even without the electron-electron spin interaction. Due to a geometric valley-orbit coupling from the Berry phase effect, the zero-point energy of electronic phonons reaches minimum when electrons are fully valley polarized. This leads to a spontaneous magnetization when below a critical temperature. We further propose engineering magnetism in Mott-Wigner crystals through the photoexcitation of chiral electronic phonons.

Twisted van der Waals (vdW) bilayers can support tunable surface/hyperbolic phonon polaritons (S/HPhPs) depending on the interlayer twist angle. S/HPhPs can be thermally excited and significantly modify the thermal near field. A photonic topological transition occurs at a critical twist angle, where the polariton dispersion switches from hyperbolic to elliptical. Because the twist angle governs the polariton modes, it is intrinsically linked to the optical helicity density (OHD) of the near-field thermal emission. In this work, a relationship between the OHD of near-field emission and the twist angle of twisted bilayer vdW materials is identified and investigated. To evaluate the OHD, a $3\times 3$ coherence-matrix method is derived from the fluctuation-dissipation theorem (FDT), which provides a complete description of the thermal electromagnetic field of the twisted bilayer and a formalism for OHD based on the polarization matrix is employed. The topological transition angle (TTA) is determined by calculating the polariton dispersion of the vdW bilayer at different twist angles. A strong correlation between the OHD and TTA is observed. This behavior is associated with polariton canalization and the asymmetric polariton modal response. In this study, we provide insights into the analysis of angular momentum in near-field thermal radiation from twisted vdW structures.

We perform an investigation of the quantum transmission in a quantum wire that is coupled locally to a nonreciprocal quantum chain. Our findings reveal that in this system, the quantum transmission properties are determined by the characteristics of the quantum chain. For the case of the Hermitian chain, it induces abundant antiresonance and bound states in continuum, governed by the length parity of the chain and the wire-chain coupling manner. Next, when nonreciprocal couplings are incorporated in the quantum chain, more Fano antiresonance points are allowed to appear in the transmission function spectra, accompanied by the disappearance of the bound states in continuum. Besides, with the lengthening of the quantum chain, the antiresonance points are transformed into a well-defined insulating band in the transmission function spectra. Further analysis suggests that except the Fano antiresonance, the occurrence of the non-Hermitian skin effect induces additional suppression of the quantum transmission, which leads to the formation of an insulating band. We conclude that this research provides valuable insights for the transmission properties in quantum systems featuring nonreciprocal couplings.

We investigate the thermodynamic properties of elemental cerium by assessing the crucial role of phonon free energy within the framework of dynamical mean-field theory (DMFT). While conventional density functional theory (DFT) often fails to capture the intricate energy landscape of $f$-electron materials, our approach integrates many-body electronic correlations with lattice dynamics to achieve a more rigorous description of the equation of state. We calculate the total energy as a function of the lattice constant at both the DFT and $\mathrm{DFT}+\mathrm{DMFT}$ levels, subsequently incorporating the vibrational free energy derived from the phonon density of states. Our findings reveal that electronic renormalization of the force constants significantly alters the phonon spectra, particularly in the strongly correlated $\gamma$ phase. By applying these phonon corrections to the energy profiles, we observe a substantial refinement in the predicted equilibrium volumes. Using principal component-based machine learning, we interpolate phonon dispersions continuously from a finite set of first-principles calculations and compare them with experiment, finding significantly closer agreement than conventional DFT and $\mathrm{DFT}+\mathrm{U}$ calculations that neglect dynamical many-body correlations. This study underlines the necessity of accounting for both electronic and vibrational entropy when evaluating the phase stability and structural transitions of lanthanide systems under varying pressures and temperatures.

Surface confined electronic states provide a fertile ground for discovering emergent phenomena that have no counterpart in the bulk, offering new routes to manipulate correlations, symmetry breaking, and dimensionality at the atomic scale. Here, we show that charge density wave (CDW) symmetry breaking can yield surface states in $1\mathrm{T}\text{−}{\mathrm{TiSe}}_2$. Micro–angle-resolved photoemission spectroscopy ($\mu$-ARPES) resolves a sharp, two-dimensional surface resonant state (SRS) that emerges within the CDW reconstructed low energy spectrum. The SRS exhibits notable temperature dependence and its spectral weight collapses around $\sim 160\mathrm{K}$, while CDW transition temperature $T_{\mathrm{CDW}}$ is commonly reported as $\approx 202\mathrm{K}$. Slab $\mathrm{DFT}+U$ calculations reproduce a surface localized resonance when CDW folding brings valence and conduction states into near degeneracy, suggesting a correlation tuned, surface selective origin. These results point to a form of correlation-tuned surface resonance in a layered CDW compound and suggest a framework for engineering low-dimensional quantum states in van der Waals materials via symmetry breaking and electronic structure tuning.

We introduce a functional renormalization group framework formulated directly in the Floquet steady state that systematically incorporates frequency-dependent interaction effects. By retaining the frequency structure of the two-particle vertex up to second order in interaction strength, our approach provides controlled access to dynamical response functions and nonequilibrium transport in driven, interacting systems. Using the periodically driven single-impurity Anderson model as a paradigmatic example, we benchmark our results against state-of-the-art Floquet Green's function methods and find quantitative agreement for finite-frequency observables up to intermediate interaction strengths. Remarkably, we also show that static properties are often captured reliably by much simpler approximations, suggesting practical pathways for modeling driven quantum materials. Finally, we demonstrate that although periodic driving of the dot strongly broadens the Kondo resonance through inelastic scattering, it leaves the many-body Kondo cloud largely intact. This robustness suppresses Floquet replicas of the Kondo peak and leads to a partial persistence of Kondo pinning, highlighting the resilience of emergent many-body correlations under local periodic driving.

Twisted bilayer hyperbolic metasurfaces provide versatile control over surface-wave dispersion via rotational stacking, enabling highly directional canalization and flexible wave-front engineering. While prior studies have mainly focused on hyperbolic eigenmodes, the behavior of antihyperbolic surface waves—characterized by distinct polarization and substantially smaller wave vectors—remains largely unexplored. Here, we investigate antihyperbolic surface waves in twisted bilayer hyperbolic metasurfaces, revealing that their isofrequency contours undergo a topological reconfiguration from open to closed at a critical twist angle. Furthermore, we find that tuning the interlayer separation of bilayer metasurfaces can induce the conversion between anisotropic and isotropic surface-wave propagation. These findings demonstrate that antihyperbolic eigenmodes can offer a method for dispersion engineering in nanophotonics, paving the way for advanced wave-front control and topological photonic devices.

Near-field radiative heat transfer (NFRHT), which can surpass the blackbody limit by orders of magnitude through evanescent waves like surface plasmon polaritons (SPPs), holds great promise for advanced thermal management and energy conversion. A central challenge is achieving dynamic, nonreciprocal control over heat flow. This work proposes a scheme for velocity-programmed nonreciprocal thermal radiation using graphene. We develop a comprehensive fluctuational-electrodynamics framework that self-consistently incorporates both macroscopic plate motion, described by Lorentz transformations, and microscopic carrier drift, captured by a nonlocal, non-reciprocal conductivity model. This dual-velocity approach allows active sculpting of the SPP dispersion in momentum space, thereby tailoring the photon-tunneling probability in a directional manner. We demonstrate that by merely adjusting the relative velocities—while maintaining both plates at an identical temperature (300 K)—the net heat flux can be continuously tuned from strong forward to strong reverse flow, passing through multiple zero-crossing points. Momentum-space analyses provide a clear physical picture: the programmable heat flux originates from the Doppler-shifted mismatch or alignment of the SPP dispersions of the two graphene sheets. This work establishes a platform for active thermal photonics, where heat flow becomes a dynamically programmable function of velocity, with implications for on-chip thermal routing, adaptive thermal management, and energy recovery systems.

We study dilute two-dimensional systems of interacting excitons with a moat dispersion, whose ground-state manifold consists of a set of discrete or continuously degenerate energy minima. At low densities and in the presence of contact interactions, it is known that the bosons can undergo statistical transmutation and give rise to a chiral spin liquid. Here, we show that long-range interactions such as those expected in excitonic systems introduce a rich competition between the chiral spin liquid and different kinds of Bose-Einstein condensates. The moat dispersion can favor Bose-Einstein condensation into states occupying multiple momenta, leading to inhomogeneous and supersolid phases with a highly anisotropic superfluid response. We demonstrate that a proper $T$-matrix renormalization of the exciton-exciton interaction is essential for describing these phases and show that they can arise even from purely repulsive interactions. This formalism is employed to obtain the phase diagram of competing homogeneous and stripe condensates with the chiral spin liquid in an electron-hole bilayer model. In addition, we show how the $T$ matrix enters the familiar Gross-Pitaevskii framework and map out extended phase diagrams within a pseudopotential approximation. We place our findings in the context of real excitonic systems by discussing the roles of finite lifetimes, disorder, band-structure warping, and nonzero temperatures. We conclude that moat bands can drive Bose-Einstein condensation and supersolidity already at weak coupling, in contrast to the case of a standard parabolic dispersion.

Our understanding of vibrations in solids currently rests on concepts and techniques designed for crystals and explicitly relying on periodicity, hence inapplicable to amorphous materials. As a consequence, no established framework enables a systematic decomposition of the vibrational spectrum of amorphous solids into contributions associated with well-defined types of atomic motions. This methodological gap obscures the interpretation of various experimental probes of linear response, based on the measurements of acoustic, thermal, or optical properties. Here, we construct such a framework—Recursive Orthogonal Splitting Analysis (ROSA)—which decomposes the vibrational space by recursive applications of the projection formalism. Each step of the procedure exploits a dominant stiffness contrast to split a vibrational displacement subspace into two weakly coupled orthogonal complements. We illustrate ROSA by applying it to the archetypal covalent glass—vitreous silica. Successively separating bond-stretching, symmetric and antisymmetric oxygen motions, isotropic and deviatoric tetrahedral strains, and distinct classes of tetrahedral bending, reveals a hierarchical structure of the space of vibrational degrees of freedom, involving six mutually orthogonal subspaces. These subspaces selectively capture all salient spectral features, including the two-humped structure in the low-frequency range, the peak near $800{\mathrm{cm}}^{-1}$, and the high-frequency doublet. In the low-frequency range, rigid-unit tetrahedral rotations do not constitute independent degrees of freedom but are kinematically enslaved to bending coordinates by no-stretch constraints. Because ROSA relies solely on the existence of contrasted stiffness scales associated with the point symmetry of local structural units, and on their separation by enforcing geometric constraints via the projection formalism, it is directly applicable to a broad class of covalent network glasses.

The zero-field magnetic ground state of the superconducting polar semimetal $\mathrm{EuAuBi}$ is determined using neutron powder diffraction. The system realizes a commensurate antiferromagnetic ground state of wave vector $\mathbf{k}=(1/3,0,0)$ with moments along the crystallographic $b$ axis and unequal moment amplitudes between the two magnetically inequivalent Eu orbits. On warming above an intermediate transition temperature, $T_{\mathrm{N}2}\approx 3.3\mathrm{K}$, a commensurate-incommensurate transition occurs with $\mathbf{k}\left(T\right)=[1/3-\delta (T),0,0]$, preserving the moment direction and occurring only within a narrow temperature window below the incommensurate-paramagnetic transition at $T_{\mathrm{N}1}\approx 4\mathrm{K}$. A minimal isotropic exchange toy model including interactions up to third-nearest neighbors suggests the presence of competing interactions. Together, these results provide a foundation for future studies of materials hosting an interplay between magnetism, superconductivity, and electric polarity.