The identification of in-plane twofold symmetry in layered superconductors has sparked considerable interest. While transport measurements often reveal pronounced anisotropy, interpretation of their origin remains challenging due to the difficulty in disentangling competing contributions. Here, we systematically investigate the challenges of resolving intrinsic twofold symmetry in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ through angular-dependent in-plane magnetoresistance measurements on exfoliated micron-scale devices. The sub-$10\text{−}\mu \mathrm{m}$ devices, with well-defined current directions, minimize contributions from structural domain walls and facilitate current-direction switching. Our experiments reveal a persistent twofold anisotropy in the upper critical field $\left(H_{\text{c}2}\right)$, whose principal axis rotates with the applied current, indicating an extrinsic origin. The anisotropy also grows with increasing current, consistent with vortex motion driven by the Lorentz force. Two-axis rotational mapping combined with theoretical calculations further reveals how field misalignment can mimic or amplify apparent in-plane anisotropy. These results suggest that if intrinsic twofold symmetry does exist, its anisotropy is likely weak and highly susceptible to extrinsic influences. Our findings highlight the necessity of multiaxis and current-swapping methodologies for probing rotational symmetry in layered superconductors, and provide a refined framework for such investigations.

In this work, we present a theory to address conflicting experimental claims regarding the charge density wave (CDW) state in ${\mathrm{TiSe}}_2$, including whether there is single or multiple CDW transitions and whether threefold rotation symmetry ($C_3$) is broken. Using a continuum $\mathit{k}·\mathit{p}$ model coupled to the CDW order parameter, we show how commonplace conduction band doping induces a nematic transition from a $C_3$-symmetric $3Q$ CDW to a $C_3$-breaking $3Q$ CDW, which is favored by the large ellipticity of the conduction bands of ${\mathrm{TiSe}}_2$. We also find that a $1Q$ stripe CDW is generically stabilized for sufficiently high electron doping. We then show how both stripe and nematic CDW states emerge self-consistently from a minimal interacting tight-binding model for both positive and negative initial gaps. Our theory provides a scenario in which, as temperature is lowered, a second $C_3$-breaking transition may occur or not, depending on the doping level, potentially explaining the experimental variability. These predictions can be further verified with a variety of probes including transport, photoemission, and tunneling.

Synchrotron x-ray diffraction measurements were performed on ${}^{57}\mathrm{Fe}_{68}{\mathrm{Pd}}_{32}$ at multiple pressures and two temperatures in a diamond-anvil cell. Between 4 and 11 GPa, the thermal expansion was zero or slightly negative. This pressure-induced Invar effect was studied further with ${}^{57}\mathrm{Fe}$ nuclear forward scattering and nuclear resonant inelastic x-ray scattering to obtain information on the pressure-induced changes in both the magnetization and the phonon density of states. Magnetic entropy and phonon entropy were obtained from these results, the latter with additional measurements from inelastic neutron scattering to account for the contributions from Pd atoms. The dependencies of these entropies on pressure gave the magnetic and phonon contributions to thermal expansion. These canceled in the region of pressure-induced Invar behavior, even though they individually increased by more than a factor of 2 below the Curie pressure. The behavior of phonons gives evidence for spin-phonon interactions in ${\mathrm{Fe}}_{68}{\mathrm{Pd}}_{32}$. A general explanation of the pressure-induced Invar effect is presented, showing that Invar behavior is typically expected at a pressure $P^{*}$ below a magnetic transition at pressure $P_{\mathrm{C}}$. The difference in pressure $P_{\mathrm{C}}-P^{*}$ scales with the fractional reduction in magnetic exchange interaction per fractional change in volume, divided by the average Grüneisen parameter.

Disorder operators are a type of nonlocal observables for quantum many-body systems, measuring the fluctuations of symmetry charges inside a region. It has been shown that disorder operators can reveal global aspects of many-body states that are otherwise difficult to access through local measurements. We study the disorder operator for U(1) (charge or spin) symmetry in two-dimensional Fermi and non-Fermi liquid states, using the multidimensional bosonization formalism. For a region $A$, the logarithm of the charge disorder parameter in a Fermi liquid with isotropic interactions scales asymptotically as $l_{A}ln{l}_A$, with $l_A$ being the linear size of the region $A$. We calculate the proportionality coefficient in terms of Landau parameters of the Fermi liquid theory. We then study models of the Fermi surface coupled to gapless bosonic fields realizing non-Fermi liquid states. In a simple spinless model, where the fermion density is coupled to a critical scalar, we find that at the quantum critical point the scaling behavior of the charge disorder operators is drastically modified to $l_A{ln}^2{l}_A$. We also consider the composite Fermi liquid state and argue that the charge disorder operator scales as $l_A$.

Shandite kagome materials have attracted great research attention due to their intriguing properties, such as the magnetic Weyl semimetal phase, endless nodal lines, and pressure-induced superconductivity. In this work, by combining angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic band structure of the shandite kagome compound $\mathrm{N}{\mathrm{i}}_3\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_2$. The measured band structure is in good agreement with ab initio calculations including the spin-orbit coupling effect. The experimental spectra are predominantly characterized by surface resonance states exhibiting highly anisotropic band dispersions near the Fermi level. These features dominate the electronic states near the Fermi level, which are likely associated with the anisotropic transport properties observed in $\mathrm{N}{\mathrm{i}}_3\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_2$. Notably, the large spin-orbit coupling in this material leads to the formation of a massive Dirac-like band dispersion in the surface resonance states, contrasting with the gapless Dirac dispersion found in the surface states of its sister compound $\mathrm{N}{\mathrm{i}}_3\mathrm{I}{\mathrm{n}}_2{\mathrm{S}}_2$. Our work will help understand the influence of the spin-orbit coupling effect on both the surface and bulk electronic states of shandite compounds. Furthermore, it establishes a foundation for exploring the potential applications of surface resonance states in surface science.

The nanomechanical and tribological properties of twisted bilayers of graphene (TBGs) and other two-dimensional (2D) structurally lubric interfaces still warrant investigation, particularly about the possibilities of spontaneous, defect-free pinning. We show here through extensive sliding simulations that TBGs remain superlubric even under loads up to 10 GPa and twist angles down to $0.3^{\circ }$, with no evidence of pinning. To understand that, we studied a 2D Frenkel-Kontorova (FK) model—a twisted monolayer lattice in a periodic potential of variable magnitude $U_0$ and stiffness $K$. Aubry-type spontaneous pinning appears at small twists, albeit with extra large $U_0/K{a}^2$, when the width $w$ of moiré dislocations shrinks to $\sim 4a$, where $a$ is the lattice spacing. A complementary FK-type model based on realistic graphene elasticity and geometry confirms that most TBGs and twisted 2D interfaces lie far below the critical pinning threshold. Their strong in-plane bonds and weak interlayer interactions yield $U_0/K{a}^2$ orders of magnitude too small, and moiré dislocations remain wide, $w\gg a$. This provides a unified theoretical framework to understand and predict Aubry pinning transitions, establishing the dislocation width as a practical criterion for spontaneous Aubry pinning, and highlighting its general absence with resilience of sliding lubricity in twisted 2D material bilayers under ordinary conditions.

Spin Seebeck effect refers to the magnonic thermal spin injection from a magnet into the adjacent heavy metal. A ferrimagnetic insulator yttrium iron garnet (YIG) is the material most studied for the spin Seebeck effect. Here, to account for a convex downward temperature dependence of the spin Seebeck effect observed in YIG/Pt system near the Curie temperature $T_C$, we develop Ginzburg-Landau theory of the spin Seebeck effect in two-sublattice ferrimagnets. We find that only when we take into account the “Néel coupling,” i.e., interfacial exchange coupling between the Néel order parameter of YIG and spin accumulation of Pt, the convex downward temperature dependence is explained. The present result sheds light on the importance of the Néel coupling in ferrimagnetic spintronics.

Geometric frustration is a key parameter controlling electronic and magnetic properties of quantum spin liquid systems, yet remains challenging to tune. Here, we coherently drive molecular vibrations with midinfrared pulses in two organic quantum spin liquid candidates, the insulating $\kappa \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_2{\mathrm{Cu}}_2{\left(\mathrm{CN}\right)}_3$ and the metallic $\kappa \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_4{\mathrm{Hg}}_{2.89}{\mathrm{Br}}_8$, and probe their electronic response through ultrafast reflectivity measurements. We observe a nonlinear coupling between local molecular vibrations and nonlocal phonons, which is expected to directly modulate the geometric frustration of their triangular lattice. Our findings establish a promising route to dynamically control frustration in nonbipartite quantum materials.

A crucial ingredient for scalable, fault-tolerant quantum computing is the construction of logical qubits with low error rates and intrinsic noise protection. We propose a cross-platform construction for such hardware-level noise protection, in which the qubits are protected from depolarizing (relaxation) and dephasing errors induced by local noise. These logical qubits arise from the entanglement between two internal degrees of freedom, hence we term them entanglemons. Our construction is based on the emergence of collective degrees of freedom from a generalized coherent state construction, similar in spirit to spin coherent states, of a set of such internally entangled units. These degrees of freedom, for a finite number of units, parametrize the quantized version of complex projective space $\mathbb{C}\mathrm{P}$(3). The noise protection of the entanglemon qubit is then a consequence of a weakly coupled emergent degree of freedom arising due to the nonlinear geometry of complex projective space. We present two simple models for entanglemons, which are platform agnostic, provide varying levels of protection, and in which the qubit-basis states are the two lowest-energy states with a higher-energy gap to other states. We end by commenting on how entanglemons could be realized in platforms ranging from superconducting circuits, and trapped ion platforms, to possibly also quantum Hall skyrmions in graphene and quantum dots in semiconductors. The inherent noise protection in our models combined with the platform agnosticism highlights the potential of encoding information in additional weakly coupled emergent degrees of freedom arising in nonlinear geometrical spaces and curved phase spaces, thereby proposing a different route to achieve scalable fault tolerance.

In order to understand how magnetic moments in a magnetic topological insulator (MTI) interact with the topological surface states (TSS) to open an exchange gap, it is crucial to experimentally distinguish the surface magnetic properties from those of the bulk. Here we achieve this for the layered van der Waals intrinsic MTI ${\mathrm{MnBi}}_6{\mathrm{Te}}_{10}$ by using x-ray absorption spectroscopy (XAS) in the surface-sensitive total electron yield (TEY) and bulk-sensitive fluorescence yield (FY) mode. The TEY data show substantial x-ray magnetic circular dichroism and x-ray magnetic linear dichroism, resulting from robust surface ferromagnetism with out-of-plane oriented Mn moments. We introduce an approach to decompose the XAS signal in a Fourier series, allowing us to extract the rather sharp resonant Mn edges, which overlap with a strong but only gradually fluctuating Te signal. We show that the experimental TEY and FY data, measured both with circular and linear light polarization, can all be fitted with a multiplet ligand field theory model with the same values for the model parameters. This reveals a close similarity between the surface and bulk electronic and magnetic properties.

Magnetic nanoparticles present two promising effects: hyperthermia, which has potential in medical treatment approaches, and magneto-optical properties, which are useful in applications such as sensing and theranostics. This study investigates the impact of the heating induced by hyperthermia on the optical and magneto-optical properties of magnetic nanoparticles. A dedicated optical setup allows one to simultaneously induce magnetic hyperthermia with an alternating magnetic field and measure optical properties as well as magneto-induced birefringence and optical absorption. We demonstrate that hyperthermia heating of ${\mathrm{CoFe}}_2{\mathrm{O}}_4$ nanoparticles induces a decrease of their magneto-optical birefringence and an increase of their absorption. These results provide noninvasive monitoring methods for in situ temperature measurement in hyperthermia that would be beneficial for several applications and solid-state measurement.

Continuous symmetries lead to universal slow relaxation of correlation functions in quantum many-body systems. In this work, we study how local symmetry-breaking impurities affect the dynamics of these correlation functions using Brownian quantum circuits, which we expect to apply to generic nonintegrable systems with the same symmetries. While explicitly breaking the symmetry is generally expected to lead to eventual restoration of full ergodicity, we find that approximately conserved quantities that survive under such circumstances can still induce slow relaxation. This can be understood using a super-Hamiltonian formulation, where low-lying excitations determine the late-time dynamics and exact ground states correspond to conserved quantities. We show that in one dimension, symmetry-breaking impurities modify diffusive and subdiffusive behaviors associated with $\mathrm{U}\left(1\right)$ and dipole conservation at late times, e.g., by increasing power-law decay exponents of the decay of autocorrelation functions. This stems from the fact that for these symmetries, impurities are relevant in the renormalization-group sense, e.g., bulk impurities effectively disconnect the system, completely modifying both temporal and spatial correlations. On the other hand, for an impurity that disrupts strong Hilbert space fragmentation, the super-Hamiltonian only acquires an exponentially small gap, leading to prethermal plateaus in autocorrelation functions which extend for times that scale exponentially with the distance to the impurity. Overall, our approach systematically characterizes how symmetry-breaking impurities affect relaxation dynamics in symmetric systems.

$B$ site ordered $5d^2$ double perovskites ($A_{2}B{B}^{\prime }{\text{O}}_6,B^{\prime }=5d^2)$ display a remarkable range of physical properties upon variation of the chosen $B$ and $B^{\prime }$ site ions. This sensitivity to chemical substitution reflects the delicate balance and profound impact of strong electronic correlation and spin-orbit coupling in such systems. We present rhenium $L_2$ and $L_3$ resonant inelastic x-ray scattering (RIXS) measurements of two such physically dissimilar materials, Mott-insultating ${\mathrm{Ba}}_2\mathrm{Y}\mathrm{Re}{\mathrm{O}}_6$ and semiconducting ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{Re}{\mathrm{O}}_6$. Despite these differences, our RIXS results reveal similar energy scales of Hund's ($J_H$) and spin-orbit coupling ($\zeta$) in the two materials, with both systems firmly in the intermediate Hund's coupling regime where $J_H/\zeta \sim 1$. However, there are clear differences in their RIXS spectra. The conductive character of ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{Re}{\mathrm{O}}_6$ broadens and obfuscates the atomic transitions within an electron-hole continuum, while the insulating character of ${\mathrm{Ba}}_2\mathrm{Y}\mathrm{Re}{\mathrm{O}}_6$ results in sharp atomic excitations. This contrast in their RIXS spectra despite their similar energy scales reflects a difference in the itinerancy-promoting hopping integral and illustrates the impact of the local crystal environment in double perovskites. Finally, $L_2$ and $L_3$ edge analyses of the atomic excitations in ${\mathrm{Ba}}_2\mathrm{Y}\mathrm{Re}{\mathrm{O}}_6$ reveal that the ordering of the low lying excited states is inverted compared to previous reports, such that the appropriate energy scales of Hund's and spin-orbit coupling are significantly modified. We present exact diagonalization calculations of the RIXS spectra at both edges which show good agreement with our results for new energy scales of $\zeta =0.290\left(5\right)\mathrm{eV}$ and $J_H=0.38\left(2\right)\mathrm{eV}$ $[J_H/\zeta =1.30\left(5\right)]$.

We demonstrate that epitaxial thin film antiferromagnet ${\mathrm{Mn}}_2\mathrm{As}$ exhibits the quench-switching effect, which was previously reported only in crystallographically similar antiferromagnetic CuMnAs thin films. Quench switching in ${\mathrm{Mn}}_2\mathrm{As}$ shows a stronger increase in resistivity, reaching hundreds of percent at 5 K, and significantly longer retention time of the metastable high-resistive state before relaxation towards the low-resistive uniform magnetic state. Qualitatively, ${\mathrm{Mn}}_2\mathrm{As}$ and CuMnAs show analogous parametric dependence of the magnitude and relaxation of the quench-switching signal. Quantitatively, relaxation dynamics in both materials show direct proportionality to the Néel temperature. This confirms that the quench switching has a magnetic origin in both materials. The presented results suggest that the antiferromagnets crystalizing in the ${\mathrm{Cu}}_2\mathrm{Sb}$ structure are well suited for exploring and exploiting the intriguing physics of highly nonuniform magnetic states associated with the quench switching.

Inhomogeneous ensembles of quantum dots (QDs) coupled to a charge reservoir are widely studied by using, e.g., electrical methods like capacitance-voltage spectroscopy. We present experimental measurements of the QD capacitance as a function of varying parameters such as ac frequency and bath temperature. The experiment reveals distinct shifts in the position of the capacitance peaks. While temperature-induced shifts have been explained by previous models, the observation of frequency-dependent shifts has not been explained so far. Given that existing models fall short in explaining these phenomena, we propose a refined theoretical model based on a master-equation approach which incorporates energy-dependent tunneling effects. This approach successfully reproduces the experimental data. We highlight the critical role of energy-dependent tunneling in two distinct regimes: at low temperatures, ensemble effects arising from energy-level dispersion in differently sized QDs dominate the spectral response; at high temperatures and frequencies, we observe a peak shift of a different nature, which is best described by optimizing the conjoint probability of successive in- and out-tunneling events. Our findings contribute to a deeper understanding of tunnel processes and the physical properties of QD ensembles coupled to a common reservoir, with implications for their development in applications such as single-photon sources and spin qubits.

We present a comprehensive study of magnetotransport in high-mobility trilayer graphene (TLG) devices under a transverse displacement field, focusing on symmetry-broken Landau levels (LLs) from monolayer-like and bilayer-like bands. A striking displacement-field-induced enhancement of the Landé $g$-factor is observed in the zeroth Landau level of the monolayer-like band, highlighting the formation of interaction-driven quantum Hall states. Additionally, we find a rich landscape of LL crossings in the Dirac gully region, accompanied by phase transitions between spin-, gully, and valley-polarized LLs. These experimental observations are successfully modeled using calculations based on optimized tight-binding parameters. Furthermore, our results reveal significant particle-hole asymmetry in the sequence of LLs in the Dirac gullies, attributed to differing $g$-factor values for electrons and holes. This asymmetry underscores the limitations of noninteracting models in capturing the complexities of multiband systems. This work provides insights into the interplay of symmetry-breaking mechanisms and enhanced interaction effects in Bernal-stacked trilayer graphene, advancing our understanding of quantum transport phenomena in multiband systems.

The $p$-orbital doublet in a honeycomb lattice is concretely studied with interacting spinless fermions at half filling. The Dirac fermions with linear dispersion at $\pm K$ valleys govern the noninteracting low-energy physics. In the weak-coupling regime, the Dirac fermions are gapped due to the spontaneous generation of mass terms through a uniform axial orbital ordering, rendering the system into the quantum anomalous Hall insulator phase with a nonzero Chern number. Surprisingly, the intermediate-strength many-particle interaction produces the intervalley coherence between $\pm K$ valleys by developing complex polar orbital orderings in a tripled Wigner-Seitz cell. This phase is shown to have a deep connection with the low-energy physical behavior described by the orbital exchange model in the Mott insulating regime. The classical ground-state manifold enjoys a continuous symmetry characterized by the intervalley coherent phase. Finally, the quantum fluctuation selects a unique ground state with emergent Kekulé orbitons through the order-by-disorder mechanism. Our findings provide insights for a direction of searching for Kekulé distortion in correlated multiorbital systems.

Building on a beyond-$GW$ many-body perturbative framework that incorporates higher-order vertex effects in the self-energy—giving rise to $T$-matrix and second-order exchange contributions—this approach is extended to now include the vertex derived in that work to the kernel in the Bethe-Salpeter equation (BSE) for the reducible polarization function. This results in a frequency-dependent interaction kernel that naturally captures random phase approximation effects, dynamical excitonic interactions, and the correlated propagation of multiple correlated electron-hole pairs that model multiexcitonic (including bi- and triexcitonic) effects, relevant for nonlinear optics and high-harmonic generation. These processes emerge as a result of including the functional derivatives of the screening and vertex with respect to the Green's function in the vertex, enabling a fully ab initio, time-dependent treatment of correlation effects. By focusing on the reducible rather than irreducible polarization function, this approach provides a computationally viable framework for capturing complex many-body interactions for calculating the self-energy, optical spectra, and electron energy loss spectroscopy. The resulting interaction kernel is relatively straightforward, clearly delineates the physical processes that are included and omitted, and has the same dimensionality as the conventional BSE kernel used in standard many-body perturbation theory implementations but is now itself frequency dependent. The method is expected to facilitate the integration of advanced many-body effects into state-of-the-art software packages, offering a universal and highly accurate framework for the description of subatomic correlations. Such advancements are crucial for the development of semiconductor, optoelectronic, superconducting, and antimatter technologies and ensuring that theoretical modeling evolves alongside exascale and accelerated computing.

Monoclinic compounds ${\mathrm{YbPt}}_5{\mathrm{B}}_2$ and ${\mathrm{LuPt}}_5{\mathrm{B}}_2$ [space group $C2/m$ (No. 12), own structure type] have been studied by means of elastic and inelastic neutron scattering experiments. The heavy fermion system ${\mathrm{YbPt}}_5{\mathrm{B}}_2$ orders antiferromagnetically below $T_{\mathrm{N}1}=7.8\mathrm{K}$ and exhibits an incommensurate magnetic structure with a temperature-dependent propagation vector, ${\vec{k}}_1=(0.194,0,-0.045;T=6\mathrm{K})$. Below $T_{\mathrm{N}2}=4.7\mathrm{K}$, a transition into a commensurate structure, ${\vec{k}}_2=(0,0,0)$, takes place. The transition at $T_{\mathrm{N}2}$ turns out to be of first order, as obvious from commensurate and incommensurate contributions to the magnetic moments around $T=T_{\mathrm{N}2}$. Rather large Yb moments, $m\left(\mathrm{Yb}\right)>3{\mu }_{\mathrm{B}}$, yet reduced due to the Kondo effect, were obtained as a result of the splitting of the ${\mathrm{Yb}}^{3+}$ eightfold-degenerate ground state into four doublets, owing to crystalline electric field (CEF) effects. Such unusually large moments in Yb systems can be explained only by an appropriate wave function ${\sum }_{i=-7/2}^{i=7/2}\pm {\alpha }_i|i/2\rangle$, ${\sum }_i{\alpha }_i^2=1$, constituting the CEF ground state doublet, which indeed was concluded from the present inelastic neutron data, considering the crystalline electric field theory. The overall CEF splitting is on the order of 44 meV, while the first excited level is located $\approx 25$ meV above the ground state.

The possibility of a strain-induced transformation from $g$-wave to $d$-wave altermagnetism was recently proposed for MnTe using a $k·p$ perturbative model. In this work, we demonstrate such a transition in CrSb for a wider array of strains, using a combination of a minimal model and first-principles calculations. Starting from a symmetry perspective, we analyze the spin elastoconductivity tensor, and determine the strain types which allow for a change in the altermagnetic symmetry. We obtain three strain directions, which allow for a $d$-wave type splitting, and one in which a net magnetic moment emerges. Using first-principles calculations in the absence of spin-orbit coupling (SOC), we confirm these symmetry predictions. Furthermore, these results do not alter qualitatively in the presence of SOC. Finally, we reveal that the resulting spin currents give rise to a spin-splitter effect of up to 5% under realistic strains of 1%, confirming strain as a powerful tool for tuning altermagnetic properties.