The thermal equilibrium properties of the spin-ice material ${\mathrm{Dy}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$, including specific heat, magnetization, and spin correlations, could be successfully reproduced by a model featuring magnetic interactions up to the third nearest neighbor and long-ranged dipolar forces. With the best-fit parameters, the model predicts an ordered ground state which breaks the cubic symmetry of the lattice. In this work, we analyze results from a neutron scattering experiment in which, instead of sharp Bragg peaks, a diffuse pattern was observed down to $300\text{mK}$, despite very slow cooling [A. M. Samarakoon et al., Phys. Rev. Res. 4, 033159 (2022)]. Using a reverse Monte Carlo approach, we find compatible spin configurations, analyze the suitability of antiferromagnetic spin chains as building blocks for the ground state, and provide various measures of correlation and calculate their energy. Our analysis suggests that, while infinitely long chains are not present in the experimental configuration, antiferromagnetic spin chains provide a good approximation of the data. There are indications of possible evidence for short-range chains, but further investigation is needed for confirmation.

We report single-pulse all-optical helicity-independent toggle switching in CoHo and CoDy alloy thin films, demonstrating a magnetization reversal mechanism distinct from previously observed ultrafast or precessional pathways. Unlike the subpicosecond switching in Gd-based ferrimagnets, we show that reversal occurs on a microsecond timescale via domain wall motion and coalescence processes. This dynamic is initiated by complete demagnetization of the Co sublattice following ultrafast laser excitation, with angular momentum transfer from the rare-earth element (Ho or Dy) leading to deterministic toggle behavior. Using both time-resolved magneto-optical Kerr effect measurements and Hall bar electrical detection, we establish that the reversal process is inherently slow and governed by domain dynamics. Complementary micromagnetic simulations support a model in which slight asymmetries induced by a spin current during the recovery from a demagnetized state guide the system toward a reversed saturated final magnetization. These results extend the class of materials that can exhibit deterministic magnetization reversal without magnetic fields or helicity, offering promising new routes for optically driven spintronic applications.

We develop the theory of the nonadiabatic phonon self-energy arising from coupling to electrons with finite linewidths using the spectral representation of Green's functions. Our formalism naturally includes the contribution from the intraband electronic transitions (as well as the interband ones) at all electron wave vectors to the phonon linewidths, which is forbidden for zone-center optical phonons if infinitesimal electron linewidths are used. As a proof of principle, we use the theory to calculate the linewidth of the doubly degenerate, zone-center optical $E_{2\mathrm{g}}$ phonons of graphene as a function of the chemical potential. The calculated phonon linewidths obtained with finite electron linewidths differ significantly from those obtained with infinitesimal electron linewidths even at low temperatures. Intraband electronic transitions play an important role in making this difference. Moreover, only the results accounting for the finite electron linewidths are in quantitative agreement with the available experimental data. The presented formalism is suitable for first-principles calculations.

Tensor network renormalization group maps study critical points of 2D lattice models like the Ising model by finding the fixed point of the RG map. In a prior work [Phys. Rev. X 15, 031047 (2025)]. we showed that by adding a rotation to the RG map, the Newton method could be implemented to find an extremely accurate fixed point. For a particular RG map (Gilt-TNR), we studied the spectrum of the Jacobian of the RG map at the fixed point and found good agreement between the eigenvalues corresponding to relevant and marginal operators and their known exact values. In this companion work, we use two further methods to extract many more scaling dimensions from this Newton method fixed point, and compare the numerical results with the predictions of conformal field theory (CFT). The first method is the well-known transfer matrix (TM), while the second method we refer to as the lattice dilatation operator (LDO). We introduce some extensions of these methods that also provide spins of the CFT operators, modulo an integer. With comparable computing resources, the TM and LDO methods perform equally well. The agreement for the scaling dimensions and spins is excellent up to $\mathrm{\Delta }=4^1{/}_8$, and reasonably good up to 2 units higher. Some of the eigenvalues of the Jacobian of the RG map can come from perturbations associated with total derivative interactions and so are not universal. In some past studies [Phys. Rev. Res. 3, 023048 (2021); Phys. Rev. E 109, 034111 (2024)] such nonuniversal eigenvalues did not appear in the Jacobian. We explain this surprising result by showing that their RG map has the unusual property that the Jacobian is equivalent to the LDO operator.

Spin liquids form fluctuating magnetic textures which have to obey certain rules imposed by frustration. These rules can often be written in the form of a Gauss law, indicating the local conservation of an emergent electric field. In reciprocal space, these emergent Gauss laws appear as singularities known as pinch points that are accessible to neutron-scattering measurements. But more exotic forms of electromagnetism have been stabilized in spin liquids, and in a few rare instances, these zero-dimensional singularities have been extended into one-dimensional pinch lines. Here we propose a simple framework for the design of pinch line spin liquids in a layered structure of two-dimensional algebraic spin liquids. A plethora of models can be build within this framework, as exemplified by several concrete examples where our theory is confirmed by simulations, and where the rank of the tensorial gauge field is continuously varied along the pinch line, opening new avenues in fractonic matter. Then we use our framework to understand how the evolution of the singularity pinch point along the pinch line can be understood as the interference pattern of two emergent electric fields. Finally, we apply our intuition on these emergent electric fields in real space to generic pinch line models beyond our layered framework and revisit the recently proposed pinch line model on the octochlore lattice.

We study the dynamical response function relevant for two-dimensional coherent nonlinear optical spectroscopy of the antiferromagnetic frustrated $J_1\text{−}{J}_3$ Heisenberg model on the square lattice within its long-range-ordered, incommensurate diagonal spiral phase. We argue that in this phase effective dipole coupling to the electric field is important, with the spin-current coupling potentially being the dominant mechanism for spin $1/2$. For this setting, we use linear spin wave theory to evaluate the leading nonlinear polarization response which is of second order in the driving field. We show that the response function features a strong antidiagonal, galvanoelectric feature. The width of this feature is set by relaxation rates beyond the noninteracting magnon picture, thereby providing access to single-magnon lifetimes within the multimagnon continuum of the response function. Moreover, the response function is shown to display various structures in the two-dimensional frequency plane related to exceptional regions of the magnon dispersion.

Gross–Neveu–Yukawa-type models such as the chiral Ising, chiral XY, and chiral Heisenberg models, serve as effective descriptions of two-dimensional Dirac semimetals undergoing quantum phase transitions into various symmetry-broken ordered states. Their relativistic quantum critical points govern the systems' physical behavior in the vicinity of the transition also at finite temperatures, which is strongly influenced by critical order-parameter and chiral fermion fluctuations. Here, we explore the effect of these fluctuations at zero and finite temperature, both in the Dirac phase and in the Mott phases with spontaneously broken symmetry. To that end, we set up a functional renormalization group approach, which allows us to systematically calculate the quantum phase diagrams and scaling behavior at and near quantum criticality. We explicitly estimate quantum critical exponents, calculate the quasiparticle weight of the chiral Dirac excitations, and determine the extent of the quantum critical fan. Furthermore, we expose a semimetallic precondensation regime where order-parameter fluctuations destroy order at finite temperature and we show the related manifestation of the Coleman–Hohenberg–Mermin–Wagner theorem. For the chiral XY model, we also expose signatures of Berezinskii–Kosterlitz–Thouless physics in a system that includes strong fermion fluctuations. In view of recent experimental developments on correlated phases in highly tunable two-dimensional Dirac materials, our work aims at a more comprehensive theoretical description of relativistic quantum criticality in semimetals, including non-Dirac liquid behavior.

In rare-earth Weyl semimetals, the correlated $f$ electrons play a crucial role in shaping the characteristics of Weyl nodes, potentially giving rise to magnetic Weyl states or correlated Weyl excitations. In this study, we investigate a recently discovered noncentrosymmetric Weyl semimetal, $R\mathrm{GaGe}$ $(R=\text{La,}\text{Ce,}\text{Pr})$. By combining density functional theory with dynamical mean-field theory, we demonstrate that the $f$ electrons in CeGaGe and PrGaGe are nearly fully localized. Concurrently, four inequivalent types of Weyl nodes emerge in spd bands. Notably, the $W_3^{\prime }$ Weyl point exhibits a pronounced chiral separation, leading to long Fermi arcs on the (001) surface. Below the magnetic transition temperature, the $f$-magnetic moments not only create new Weyl point $W_4^{\prime }$, but they also induce displacement of other Weyl nodes, resulting in anomalous Hall conductance. $W_4^{\prime }$ and $W_3^{\prime }$ generate double Fermi arcs on the (001) surface, which remain distinctly separated from bulk states, facilitating future experimental detection. Under volume compression, the $f$ electrons in CeGaGe progressively become itinerant and begin to obscure the Weyl nodes, making them difficult to resolve within a single-particle framework. However, upon heating beyond a critical temperature, the $f$ electrons regain localization, and the Weyl state can once again be effectively described. These findings indicate that in the $R\mathrm{GaGe}$ system, temperature and pressure can be utilized to drive intriguing transitions among paramagnetic Weyl semimetals, magnetic Weyl semimetals, and correlated Weyl semimetals.

Metallic kagome lattices are attracting significant attention as they provide a platform to explore the interplay between topology and magnetism. Angle-resolved photoemission spectroscopy (ARPES) plays a key role in unraveling their electronic structure. However, the analysis is often challenging due to the presence of multiple bands near the Fermi level. Indeed, each orbital generates three bands in a kagome lattice due to its three sites motif, which soon becomes complicated if many orbitals are present. To address this complexity, using ARPES matrix elements can be highly beneficial. First, band symmetry can be determined through selection rules based on light polarization. We emphasize that, in kagome lattices, as in all multisite lattices, symmetry of the Bloch state is not only determined by the orbital character but also by the relative phase between the three sublattices. Additionally, interference between the three sublattices leads to a strong modulation of ARPES intensity across neighboring Brillouin zones. We show how unfolded band calculations capture these modulations, helping with band identification. We apply these ideas to CoSn, whose simple structure retains the key features of a kagome lattice. Using polarization dependent ARPES in several Brillouin zones, we isolate the dispersion of each band and discuss novel correlation effects, selectively renormalizing the bands crossing the Fermi level and shifting the others.

We investigate an SU(3) Fermi-Hubbard model on a hypercubic lattice at finite temperatures, combining dynamical mean-field theory with continuous-time quantum Monte Carlo simulations. Taking strong correlations into account carefully, we find a ferromagnetically ordered state, in which one of the three components becomes dominant, when holes are doped away from one-third filling. Furthermore, we demonstrate that this ferromagnetically ordered phase undergoes a first-order transition to a paramagnetic state. We clarify the stability of the ferromagnetically ordered state against interaction strength, hole doping, and temperatures. The relevance of generalized Nagaoka ferromagnetism is also addressed, by comparing the results on the Bethe lattice.

Optical orientation of free charge carriers in semiconductors can lead to the spin orientation of carriers localized on impurities due to the exchange interaction between them. In this work we demonstrate that this effect can result in the photoconductivity dependence on the degree of circular polarization of the exciting light. The presented theory explains the photoconductivity observed in n-type GaAs at low temperatures, which depends on the value of the average electron spin, but not on its sign and decreases in a weak magnetic field perpendicular to the direction of incident radiation. Comparison of calculations with experimental data allows to estimate the parameters of spin-dependent scattering on neutral impurities, which are difficult to determine from other experiments. It is shown that the parameters of materials that determine their spin properties can be found from simple electrical measurements and without applying an external magnetic field.

The edge structure of a gate-defined compressible quantum Hall fluid in the filling fraction range $\frac{2}{3}$ to 1 is studied using the three reconstructed $e^2/3h$ fractional edge modes of a unity filling integer quantum Hall state. We find that the individually excited partially resolved $e^2/3h$ edge modes of the bulk state equilibrate completely even at higher magnetic field when passing through the gate-defined compressible fluid with filling between $\frac{2}{3}$ and 1. This result is unexpected because edge reconstruction at the smooth boundary is generally expected due to dominant incompressibility at filling $\frac{2}{3}$ and $\frac{1}{3}$. Recently, such a reconstructed edge mode has been reported for the compressible fluid in the filling fraction range $\frac{1}{3}$ to $\frac{2}{3}$. In contrast, equilibration of fractional edge modes in the compressible fluid within the filling fraction range $\frac{2}{3}$ to 1 becomes faster with increasing magnetic field. This anomalous result will stimulate further investigations on edge structure in these complex many-body systems.

Chiral metasurfaces, supported by photonic bound states in the continuum (BICs), provide a novel platform for studying chiral light-matter interactions. However, achieving near-unity chirality and ultrahigh Q factors simultaneously in dielectric metasurfaces remains a significant challenge. Here, we propose a planar chiral dielectric metasurface featuring tilted holes driven by the half-integer topological charge. This design decouples the circular dichroism (CD) and Q factors and achieves both near-unity CD and ultrahigh Q factors. We exploit the properties of the half-integer topological charge to stabilize one of the C points near the $\mathrm{\Gamma }$ point despite variations in the hole width. This provides an additional degree of freedom for independently tuning Q factors without compromising the near-unity CD values. Furthermore, the metasurface exhibits unparalleled robustness against variations in tilt angle, maintaining near-unity CD ($>0.95$) over the range of $11.{74}^{\circ }$, which extends to $25.1^{\circ }$ when perturbations are introduced to two adjacent sides. Moreover, the metasurface demonstrates a superchiral field enhancement greater than ${10}^3$. These findings highlight the potential of our design for applications requiring near-unity CD and ultrahigh Q factors, providing a practical solution to the longstanding challenge of decoupling Q factors and near-unity chirality in chiral metasurfaces.

Symmetry-protected topological phases host gapless modes at their boundary with a featureless environment of the same dimension or a trivial vacuum. In this study, we explore their behavior in a higher-dimensional environment, which itself is nontrivial—a topological vacuum. In particular, we embed a one-dimensional topological wire within a two-dimensional Chern insulator, allowing the zero-dimensional edge modes of the wire to interplay with the surrounding chiral boundary states created by the environment. In contrast to a trivial vacuum, we show, depending on the nature of low-energy modes, the topology of the environment selectively influences the topological phase transitions of the wire. Interestingly, such selectivity leads to scenarios where the environment trivializes the wire and even induces topological character in an otherwise trivial phase—an example of “proximity-induced topology.” Using both numerical and analytical approaches, we establish the general framework of such embedding and uncover the role of symmetries in shaping the fate of low-energy theories. Our findings provide a deeper understanding of heterostructural topological systems, paving the way for their experimental exploration.

We introduce a modified two-dimensional toric code Hamiltonian that exhibits explicit anyon confinement along a single spatial direction. By bounding the motion of these confined anyons, we obtain dipolar excitations with restricted mobility. We analyze the resulting logical operators, whose existence depends on the system size, as well as the structure of gapped boundaries and a tensor network representation of the ground state. Furthermore, when confinement is enforced in both directions, fractal-like excitations emerge, resulting in unpaired logical operators. We extend our construction to three-dimensional models, such as the surface code and the $X$-cube model, leading to novel dipole-loop and dipole-planon excitations that arise from bounding confined excitations. These modifications are implemented through group cohomological twistings-projective representations of finite groups-with most examples based on ${\mathbb{Z}}_2\times {\mathbb{Z}}_2$.

We consider chiral, generally nonlinear density waves in one dimension, modeling the bosonized edge modes of a two-dimensional fermionic topological insulator. Using the coincidence between bosonization and Lie-Poisson dynamics on an affine U(1) group, we show that wave profiles which are periodic in time produce Berry phases accumulated by the underlying fermionic field. These phases can be evaluated in closed form for any Hamiltonian, and they serve as a diagnostic of nonlinearity. As an explicit example, we discuss the Korteweg–de Vries equation, viewed as a model of nonlinear quantum Hall edge modes.

We derive a parton mean-field Hamiltonian for Rydberg excitations on a honeycomb lattice with nearest and density-dependent, complex next-nearest neighbor hopping. Numerical results obtained from exact diagonalization of small systems have given indications for a ground state that is a chiral spin liquid (CSL) [Phys. Rev. Res. 5, 013157 (2023)]. Here we provide further evidence for this. Calculating the ground-state wavefunction self-consistently, we show that the mean-field Hamiltonian fulfills the requirements for a CSL ground state, resulting from a projected symmetry group classification and verify the expected twofold topological degeneracy on a torus. Furthermore we find very good overlap with the ground-state wavefunctions obtained by exact diagonalization of the original Hamiltonian.

We study a type-II GaAs/AlAs quantum dot system that enables intervalley coupling between electronic states in the $\mathrm{\Gamma }$ and $X_z$ valleys, probed optically at the single-dot level. This structure intrinsically supports both direct and indirect excitons, with their spatial separation tunable via an external electric field. Stark shift spectroscopy reveals a clear double anticrossing in the neutral exciton line as a direct signature of intervalley coupling. Experimental observations, including measurements of static dipole moments and electron $g$ factors, confirm electron confinement within the AlAs barrier and highlight the involvement of barrier-localized states. We further propose that these states may contribute to the formation of multicharged excitonic complexes. A simplified model allows us to estimate the interfacial coupling strength from the measured anticrossing amplitudes.