Recently there is a report of the experimental signatures of a fractional quantum spin hall (FQSH) state at hole filling $n=3$ in a twisted ${\mathrm{MoTe}}_2$ bilayer. Previous theories of FQSH phases simply considered a decoupled pair of a fractional quantum Hall phase and its time reversal partner. Here, we show the first construction of an FQSH phase beyond the decoupling picture. We consider a pair of half-filled $C=\pm 1$ Chern bands in the two valleys, similar to the well-studied quantum Hall bilayer, but now with opposite chiralities. Because of the strong intervalley repulsion, we expect a charge gap to open with low-energy physics dominated by the neutral intervalley excitons. However, the presence of an effective “flux” frustrates exciton condensation by proliferating vortices. Here, we construct a vortex liquid of excitons dubbed a vortex spin liquid, formed from exciton pairing of the composite fermions in the decoupled composite Fermi liquid phase. This insulator is a quantum spin liquid with gapless spin excitations carried by the flux of an emergent $U(1)$ gauge field. Additionally, there exist neutral and spinless Fermi surfaces formed by fermionic vortices of a nearby intervalley-coherent order. Unlike a conventional Mott insulator, the vortex spin liquid phase also exhibits a quantized FQSH effect with gapless helical charge modes along the edge. Our work demonstrates the possibility of nontrivial FQSH phases and provides predictions to detect them in future experiments.

Confinement is a pivotal phenomenon in numerous models of high-energy and statistical physics. In this study, we investigate the emergence of confined meson excitations within a one-dimensional system, comprising Rydberg-dressed atoms trapped and coupled to a cavity field. This system can be effectively represented by an Ising-Dicke Hamiltonian model. The observed ground-state phase diagram reveals a first-order transition from a ferromagnetic-subradiant phase to a paramagnetic-superradiant phase. Notably, a quench near the transition point within the ferromagnetic-subradiant phase induces meson oscillations in the spins and leads to the creation of squeezed-vacuum light states. We suggest a method for the photonic characterization of these confined excitations, utilizing homodyne detection and single-site imaging techniques to observe the localized particles. The methodologies and results detailed in this Letter are feasible for implementation on existing cavity-QED platforms, employing Rydberg-atom arrays in deep optical lattices or optical tweezers.

The classical Landau-Lifshitz equation—the simplest model of a ferromagnet—provides an archetypal example for studying transport phenomena. In one-spatial dimension, integrability enables the classification of linear and nonlinear mode spectrum. An exact characterization of finite-temperature thermodynamics and transport has nonetheless remained elusive. We present an exact description of thermodynamic equilibrium states in terms of interacting modes. This is achieved by retrieving the classical Landau-Lifschitz model through the semiclassical limit of the integrable quantum spin-$S$ anisotropic Heisenberg chain at the level of the thermodynamic Bethe ansatz description. In the axial regime, the mode spectrum comprises solitons with unconventional statistics, whereas in the planar regime we find two additional types of modes of radiative and solitonic type. Our framework enables analytical study of unconventional transport properties: as an example we study the finite-temperature spin Drude weight, finding excellent agreement with Monte Carlo simulations.

In the last decade, chirality-induced spin selectivity (CISS) has undergone intensive study. However, there remain several critical issues, such as the microscopic mechanism of CISS, especially transverse CISS where electrons are injected perpendicular to the helix axis of chiral molecules, quantitative agreement between experiments and theory, and at which level the molecular handedness is key to the CISS. Here, we address these issues by performing a combined experimental and theoretical study on conducting polyaniline helical nanofibers which are synthesized in the absence of any chiral species. Large spin polarization is measured in both left- and right-handed nanofibers for electrons injected perpendicular to their helix axis, and it will be reversed by switching the nanofiber handedness. We first develop a theoretical model to study this transverse CISS and quantitatively explain the experiment. Our results reveal that our theory provides a unifying scheme to interpret a number of CISS experiments, quantitative agreement between experiments and numerical calculations can be achieved by weak spin-orbit coupling, and the supramolecular handedness is sufficient for spin selectivity without any chiral species.

We present techniques for performing two-qubit gates on Gottesman-Kitaev-Preskill (GKP) codes with finite energy, and find that operations designed for ideal infinite-energy codes create undesired entanglement when applied to physically realistic states. We demonstrate that this can be mitigated using recently developed local error-correction protocols, and evaluate the resulting performance. We also propose energy-conserving finite-energy gate implementations which largely avoid the need for further correction.

Topological surface states are unique to topological materials and are immune to disturbances. In isostatic lattices, mechanical topological floppy modes exhibit softness depending on the polarization relative to the terminating surface. However, in three dimensions, the polarization of topological floppy modes is disrupted by the ubiquitous mechanical Weyl lines. Here, we demonstrate, both theoretically and experimentally, the fully polarized topological mechanical phases free of Weyl lines. Floppy modes emerge exclusively on a particular surface of the three-dimensional isostatic structure, leading to the strongly asymmetric stiffness between opposing boundaries. Additionally, uniform soft strains can reversibly shift the lattice configuration to Weyl phases, switching the stiffness contrast to a trivially comparable level. Our work demonstrates the fully polarized topological mechanical phases in three dimensions, and paves the way towards engineering soft and adaptive metamaterials.

Understanding electron-phonon coupling in noncentrosymmetric materials is critical for controlling the internal fields which give rise to Rashba interactions. We apply time- and angle-resolved photoemission spectroscopy (trARPES) to study coherent phonons in the surface and bulk regions of the polar semiconductor BiTeCl. Aided by ab initio calculations, our measurements reveal the coupling of out-of-plane $A_1$ modes and an in-plane $E_2$ mode. By considering how these modes modulate the electric dipole moment in each unit cell, we show that the polar $A_1$ modes are more effectively screened in the metallic surface region, while the nonpolar $E_2$ mode couples in both regions. In addition to informing strategies to optically manipulate Rashba interactions, this Letter has broader implications for the behavior of electron-phonon coupling in systems characterized by inhomogeneous dielectric environments.

Classical spin liquids (CSLs) have proved to be a fruitful setting for the emergence of exotic gauge theories. Vacancy clusters in CSLs can introduce gauge charges into the system, and the resulting behavior in turn reveals the nature of the underlying theory. We study these effects for a series of CSLs on the honeycomb lattice. We find that dilution leads to the emergence of effective free spins with tuneable, and generally irrational, size. For a specific higher-rank CSL, described by a symmetric tensor gauge fields, dilution produces nondecaying spin textures with a characteristic quadrupolar angular structure and infinite-ranged interactions between dilution clusters.

Single-file diffusion is a paradigmatic model for the transport of Brownian colloidal particles in narrow one-dimensional channels, such as those found in certain porous media, where the particles cannot cross each other. We consider a system where a different external uniform potential is present to the right and left of an origin. For example, this is the case when two channels meeting at the origin have different radii. In equilibrium, the chemical potential of the particles are equal, the density is thus lower in the region with the higher potential, and by definition there is no net current in the system. Remarkably, a single-file tracer particle initially located at the origin, with position denoted by $Y(t)$, exhibits an average uphill drift toward the region of highest potential. This drift has the late time behavior $⟨Y(t)⟩=C{t}^{1/4}$, where the prefactor $C$ depends on the initial particle arrangement. This surprising result is shown analytically by computing the first two moments of $Y(t)$ through a simple and physically illuminating method, and also via extensive numerical simulations.

Although higher-order interactions are known to affect the typical state of dynamical processes giving rise to new collective behavior, how they drive the emergence of rare events and fluctuations is still an open problem. We investigate how fluctuations of a dynamical quantity of a random walk exploring a higher-order network arise over time. In the quenched case, where the hypergraph structure is fixed, through large deviation theory we show that the appearance of rare events is hampered in nodes with many higher-order interactions, and promoted elsewhere. Dynamical fluctuations are further boosted in an annealed scenario, where both the diffusion process and higher-order interactions evolve in time. Here, extreme fluctuations generated by optimal higher-order configurations can be predicted in the limit of a saddle-point approximation. Our study lays the groundwork for a wide and general theory of fluctuations and rare events in higher-order networks.

We entangle two cotrapped atomic barium ion qubits by collecting single visible photons from each ion through in vacuo 0.8 NA objectives, interfering them through an integrated fiber beam splitter and detecting them in coincidence. This projects the qubits into an entangled Bell state with an observed fidelity lower bound of $F>94\%$. We also introduce an ytterbium ion for sympathetic cooling to remove the need for recooling interruptions and achieve a continuous entanglement rate of $250{\mathrm{s}}^{-1}$.

It is shown that a 2D conformal field theory consisting of a central charge $c$ Liouville theory, a chiral level one, rank $N$ Kac-Moody algebra, and a weight $-3/2$ free fermion holographically generate 4D maximal helicity violating tree-level scattering amplitudes. The correlators of this 2D conformal field theory give directly the 4D leaf amplitudes associated to a single hyperbolic slice of flat space. The 4D celestial amplitudes arise in a large-$N$ and semiclassical large-$c$ limit, according to the holographic dictionary, as a translationally invariant combination of leaf amplitudes. A step in the demonstration is showing that the semiclassical limit of Liouville correlators are given by contact 3D anti–de Sitter Witten diagrams.

The effective central charge (denoted by $c_{\mathrm{eff}}$) is a measure of entanglement through a conformal interface, while the transmission coefficient (encoded in the coefficient $c_{LR}$ of the two-point function of the energy-momentum tensor across the interface) is a measure of energy transmission through the interface. It has been pointed out that these two are generally different. In this Letter, we propose the inequalities, $0\le c_{LR}\le c_{\mathrm{eff}}\le \min (c_L,c_R)$. They have the simple but important implication that the amount of energy transmission can never exceed the amount of information transmission. We verify them using the AdS/CFT correspondence, using the perturbation method, and in examples beyond holography. We also show that these inequalities are sharp by constructing a class of interfaces that saturate them.

Rydberg atoms in optical lattices and tweezers is now a well-established platform for simulating quantum spin systems. However, the role of the atoms’ spatial wave function has not been examined in detail experimentally. Here, we show a strong spin-motion coupling emerging from the large variation of the interaction potential over the wave function spread. We observe its clear signature on the ultrafast many-body nanosecond-dynamics of atoms excited to a Rydberg $S$ state, using picosecond pulses, from an unity-filling atomic Mott-insulator. We also propose an approach to tune arbitrarily the strength of the spin-motion coupling relative to the motional energy scale set by trapping potentials. Our work provides a new direction for exploring the dynamics of strongly correlated quantum systems by adding the motional degree of freedom to the Rydberg simulation toolbox.

Thermalization of radiation by contact to matter is a well-known concept, but the application of thermodynamic methods to complex quantum states of light remains a challenge. Here, we observe Bose-Einstein condensation of photons into the hybridized ground state of a coupled four-site ring potential. In our experiment, the periodically closed ring lattice superimposed by a weak harmonic trap for photons is realized inside a spatially structured dye-filled microcavity. Photons thermalize to room temperature, and above a critical photon number macroscopically occupy the symmetric linear combination of the site eigenstates with zero phase winding, which constitutes the ground state of the system. The mutual phase coherence of photons at different lattice sites is verified by optical interferometry.

The recent discovery of superconductivity in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ with $T_{\mathrm{c}}\simeq 80\mathrm{K}$ under high pressure opens up a new route to high-$T_{\mathrm{c}}$ superconductivity. This material realizes a bilayer square lattice model featuring a strong interlayer hybridization unlike many unconventional superconductors. A key question in this regard concerns how electronic correlations driven by the interlayer hybridization affect the low-energy electronic structure and the concomitant superconductivity. Here, we demonstrate using a cluster dynamical mean-field theory that the interlayer electronic correlations (IECs) induce a Lifshitz transition resulting in a change of Fermi surface topology. By solving an appropriate gap equation, we further show that the leading pairing instability, $s\pm$ wave, is enhanced by the IECs. The underlying mechanism is the quenching of a strong ferromagnetic channel, resulting from the Lifshitz transition driven by the IECs. Based on this picture, we provide a possible reason of why superconductivity emerges only under high pressure.

Motivated by very recent experimental observations of the $1/9$-magnetization plateaus in ${\mathrm{YCu}}_3{(\mathrm{OH})}_{6+x}{\mathrm{Br}}_{3-x}$ and ${\mathrm{YCu}}_3{(\mathrm{OD})}_{6+x}{\mathrm{Br}}_{3-x}$, our study delves into the magnetic-field-induced phase transitions in the nearest-neighbor antiferromagnetic Heisenberg model on the kagome lattice using the variational Monte Carlo technique. We uncover a phase transition from a zero-field Dirac spin liquid to a field-induced magnetically disordered phase that exhibits the $1/9$-magnetization plateau. Through a comprehensive analysis encompassing the magnetization distribution, spin correlations, chiral order parameter, topological entanglement entropy, ground-state degeneracy, Chern number, and excitation spectrum, we pinpoint the phase associated with this magnetization plateau as a chiral ${\mathbb{Z}}_3$ topological quantum spin liquid and elucidate its diverse physical properties.

The efficient detection of the Néel vector in antiferromagnets is one of the prerequisites toward antiferromagnetic spintronic devices and remains a challenging problem. Here, we propose that the layer Hall effect can be used to efficiently detect the Néel vector in centrosymmetric magnetoelectric antiferromagnets. Thanks to the robust surface magnetization of magnetoelectric antiferromagnets, the combination of sizable exchange field and an applied electric field results in the layer-locked spin-polarized band edges. Moreover, the Berry curvature can be engineered efficiently by an electric field, which consequently gives rise to the layer-locked Berry curvature responsible for the layer Hall effect. Importantly, it is demonstrated that the layer Hall conductivity strongly depends on the Néel vector orientation and exhibits rich electromagnetic responses, which can be used to detect the Néel vector reversal. Based on density functional theory calculations, we exemplify those phenomena in the prototypical ${\mathrm{Cr}}_2{\mathrm{O}}_3$ compound. A complete list of the magnetic point groups sustaining the layer Hall effect is presented, aiding the search for realistic materials. Our work proposes a novel approach to detect the Néel vector and holds great promise for antiferromagnetic spintronic applications.