We experimentally demonstrate that the spin state (up or down) of circularly polarized light can be reliably encoded as a polar structural state (up or down) in chiral liquid crystals, with high selectivity. This enables a spin-driven, nonvolatile binary liquid crystal memory, which can be optically written and electrically erased on demand. The underlying mechanism involves an orientational buckling instability, whose direction depends on whether the handedness of light matches or opposes that of the chiral medium. This optical poling effect arises from a chiral light-matter interaction during the propagation of light through the twisted anisotropic medium.

It is by now well known, that at thermal equilibrium, the dynamics of multimoded optical configurations eventually settle into a Rayleigh-Jeans (RJ) distribution in the presence of weak nonlinearities. Yet, in spite of intense research, a general methodology to quantify and predict the complete statistical response of optical microcanonical settings remains elusive. Toward this end, we here develop a universal theory of fluctuation statistics for nonlinear multimode optical systems. Our results reveal a transition from narrow quasi-Lorentzian statistics in the low temperature regime, to an exponential distribution at higher temperatures. We show that this peculiar morphing of the underlying photostatistics is unique to microcanonical systems and has no analog in grand canonical configurations. A comparison between direct phase space integration and numerical simulations shows excellent agreement with our theoretical results, providing a testament to ergodicity even in nonlinear systems with very few modes. Through our formal methodology, we are able to accurately quantify the nonlinear equilibria of small sized configurations, demonstrating a strong deviation from RJ statistics and an equilibrium response that defies equipartition at infinite temperatures.

Recent angle-resolved photoelectron spectroscopy (ARPES) measurements of the hole effective mass in ${\mathrm{CsPbBr}}_3$ revealed an enhancement of $\sim 50\%$ compared to the bare mass computed from first principles for ${\mathrm{CsPbBr}}_3$ at $T=0\mathrm{K}$. This large enhancement was interpreted as evidence of polaron formation. Employing accurate finite-temperature first-principles calculations, we show that the calculated hole effective mass of ${\mathrm{CsPbBr}}_3$ at $T=300\mathrm{K}$ can explain experimental results without invoking polarons. Thermal fluctuations are particularly strong in halide perovskites compared to conventional semiconductors such as Si and GaAs, and cannot be ignored when comparing with experiment. We not only resolve the debate on polaron formation in halide perovskites, but also demonstrate the general importance of including thermal fluctuations in first-principles calculations for strongly anharmonic materials.

A domain-wall pump by an extended cluster model of $S=1/2$ spins is proposed with local U(1) gauge invariance. In contrast to the conventional pump, the current and the gauge field are defined on sites instead of links. Its snapshot ground state is gapped and doubly degenerated due to ${\mathbb{Z}}_2$ invariance, which is broken by an infinitesimal boundary magnetic field. The ground state associated with the spontaneous symmetry breaking is, at the same time, symmetry-protected with additional spatial inversion that is characterized by the ${\mathbb{Z}}_2$ Berry phase defined by the twist on the boundary site. We investigate the topological domain-wall pump with and without boundaries. The topological pump associated with the inversion symmetry-breaking path induces a nontrivial Chern number of bulk and a singular behavior of edge states of the domain wall. Generalization to the multispin interaction is also explicitly given. These extended quantum degrees of freedom are prominent qubits that are topologically protected.

Altermagnets exhibit nonrelativistic spin splitting due to the breaking of time-reversal symmetry and have been garnering significant attention as promising materials for spintronic applications. In contrast, conventional antiferromagnets without spin splitting seem to not have any symmetry breaking and have drawn less attention. However, we show that conventional antiferromagnets with a nonzero propagation vector ($\mathit{Q}$ vector) bring about nontrivial symmetry breakings. The incompatibility between the $\mathit{Q}$ vector and nonsymmorphic symmetry leads to macroscopic symmetry breaking without lifting spin degeneracy. Moreover, the hidden altermagnetic spin splitting in the electronic structure gives rise to various emergent responses. To examine our prediction, we perform first-principles calculations for ${\mathrm{MnS}}_2$ and investigate its multiferroic properties, such as nonlinear transport and optical activity. Our findings reveal unique properties in conventional antiferromagnets, providing another perspective for designing spintronic materials.

The novel kagome family $R{\mathrm{Ti}}_3{\mathrm{Bi}}_4$ ($R$: rare-earth metals) offers a unique platform for exploring distinctive physical phenomena such as anisotropy, spin density wave, and anomalous Hall effect. In particular, the magnetic frustration and behavior of magnetic anisotropy in antiferromagnetic (AFM) kagome materials are of great interest for the fundamental studies and hold promise for next-generation device applications. Here, we report a tunable bifurcation of magnetic anisotropic and bi-oriented AFM order observed in the quasi-1D kagome antiferromagnet ${\mathrm{GdTi}}_3{\mathrm{Bi}}_4$. The magnetic domain evolutions during two plateau transition processes are directly visualized, unveiling a pronounced in-plane anisotropy along the $a$ axis. Temperature-dependent characterization reveals a bifurcation transition of anisotropy at approximately 2 K, where the $a$-axis anisotropy splits into two special orientations, revealing a hidden bi-oriented in-plane AFM order that deviates from the high-symmetry direction by $\pm 7°$. More intriguingly, the characteristics of the bifurcated anisotropy are clearly illustrated through vector magnetic field modulation, revealing three distinct in-plane domain phases in the transverse magnetic field phase diagram. Our results not only provide valuable insights into the tunable bifurcation of magnetic anisotropic in ${\mathrm{GdTi}}_3{\mathrm{Bi}}_4$, but also pave a novel pathway for AFM spintronics development.

We report on the utilization of Si in plasmonics research, specifically targeting deep ultraviolet (DUV) applications. By incorporating periodic submicron gratings on a Si surface, we demonstrate a photoconductive Si detector with significantly enhanced responsivity to DUV light, which is achieved via surface plasmon resonance (SPR). Notably, even without a metal, the detector exhibits improved responsivity only under TM-polarized light, supporting the interpretation that Si excites SPR. Our demonstration not only validates the effectiveness of Si plasmonics for enhancing photodetector performance but also introduces innovative techniques with potential applications in various research fields.

The tomographic Fermi liquid (TFL) hypothesis posits starkly different relaxation times for odd and even angular harmonics of electron distribution function in two-dimensional systems, but its experimental verification remains elusive. Traditional electrical transport struggles to discern these lifetimes, as resistivity is largely unaffected by electron scattering. Here, we demonstrate that high-order cyclotron resonance (CR) offers a direct probe: The linewidth of the $m$th CR peak directly reflects the relaxation rate ${\gamma }_m=1/{\tau }_m$ of the corresponding angular harmonic. Combining theory and terahertz photoconductivity measurements in graphene, we show that the third-order CR exhibits a narrower linewidth than the second-order CR, yielding ${\tau }_3>{\tau }_2$. This hierarchy defies conventional impurity or phonon scattering models, instead aligning with TFL predictions where odd harmonics evade relaxation via head-on collisions. Our results provide definitive evidence for the TFL regime and establish high-order CR as a powerful tool to unravel hydrodynamic transport in quantum materials.

We present a first principles strategy for developing approximations for excited states through ensemble density functionals. Central to our result is the recognition that density-driven correlations (ddc’s) can be vitally important to address excited states individually through ensembles, yet standard density-functional approximations based on ground state physics miss ddc’s altogether. To model the ddc, we exploit the recently understood low-density limit of electrons in excited states. The theory developments are then combined to produce a proof-of-concept excited state approximation that resolves urgent paradigmatic failures (double excitations, charge transfer excitations, piecewise linearity) of existing state-of-art density-functional approaches, directly from differences in self-consistent field calculations; i.e., $\mathrm{\Delta }\mathrm{SCF}$. In light of its observed impressive performance, we conclude that the approach represents a major step toward unified and accurate modeling of neutral and charged excitations.

We perform a structural analysis of large scale jammed packings of monodisperse, frictionless and frictional spheres to elucidate structural signatures of the static structure factor in the low-to-intermediate wave number region. We employ discrete element method simulations containing up to $8\times {10}^7$ particles, in which the particle friction coefficient(s), including sliding, rolling, and twisting interactions, are varied. At intermediate wave number values, corresponding to length scales that lie between that of the nearest neighbor primary peak and the system size, we find the emergence of a prepeak—a signature of intermediate range order—that grows with increasing friction. We correlate the emergence of this peak to real space fluctuations in the local particle coordination number, which exhibits a grainy fluctuating field throughout the packing process that is retained in the final, mechanically stable state. While the formation of the prepeak shows varying degrees of robustness to packing protocol changes, our results suggest that preparation history may be used to construct packings with variable large length scale structural properties.

The Goldman-Hodgkin-Katz (GHK) theory has been the paradigm for ion transport in physiological systems for the past century. However, GHK incorrectly assumes a uniform electrical field, leading to several inconsistencies. We propose a new theory developed using methods from the reverse-electrodialysis (RED) community. Our theory, substantiated by simulations, provides expressions for all the main characteristics of ion transport and connects GHK to RED, providing a remarkably robust framework for (re-)interpreting ion transport experiments in any (living or inanimate) charge-selective system.

We study the emergence of decoherent histories in isolated systems based on exact numerical integration of the Schrödinger equation for a Heisenberg chain. We reveal that the nature of the system, which we switch from (i) chaotic to (ii) interacting integrable to (iii) noninteracting integrable, strongly impacts decoherence of coarse spin observables. From a finite size scaling law we infer a strong exponential suppression of coherences for (i), a weak exponential suppression for (ii), and no exponential suppression for (iii) on a relevant short (nonequilibrium) timescale. Moreover, for longer times we find stronger decoherence for (i) but the opposite for (ii), hinting even at a possible power-law decay for (ii) at equilibrium timescales. This behavior is encoded in the multitime properties of the quantum histories and it can not be explained by environmentally induced decoherence. Our results suggest that chaoticity plays a crucial role in the emergence of classicality in finite size systems.

Neutrino telescopes, including IceCube, can detect galactic supernova events by observing the collective rise in photomultiplier count rates with a subsecond time resolution. Leveraging precise timing, we demonstrate for the first time the ability of neutrino telescopes to explore new weakly coupled states emitted from supernovae and subsequently decaying to neutrinos. Our approach utilizes publicly available packages, asteria and snewpy, for simulating detector responses and parametrizing neutrino fluxes originating from the standard model and new physics. We present results for two beyond-the-standard model scenarios and introduce the tool developed for testing a diverse range of new physics models.

I present a highly efficient integration method for scattering calculations, and a “partial rate matrix” that encodes the scattering rate as a function of the SO(3) orientation of the detector. This replaces the original multidimensional rate integral with a simple exercise in vector multiplication, speeding up the rate calculation by a factor of around ${10}^8$. I include a scheme to fully factorize the dark matter particle model, its astrophysical velocity distribution, and the properties of the target material from each other, enabling efficient calculation of the partial rate matrix even in studies comparing large sets of these input functions. This is now the only sensible way to evaluate the dark matter scattering rate in anisotropic detector materials. It is straightforward to generalize this method to other difficult but linear problems.

It is a long-standing puzzle why the $CP$ violation (CPV) in the baryon system has not yet been definitively established as in the meson one. We demonstrate that individual partial-wave CPV in the ${\mathrm{\Lambda }}_b\to p{\pi }^{-}$ and $p{K}^{-}$ decays can exceed 10%, but the destruction between the partial waves (the suppression by the small partial-wave weight) results in a small net direct CPV in the former (the latter) as measured currently. Our finding highlights the different dynamics responsible for CPVs in baryon and meson decays. We propose to probe the CPV observables associated with the angular distributions of the ${\mathrm{\Lambda }}_b\to p{a}_1(1260)$, $p{K}_1(1270)$ decay products, which are large enough for being identified experimentally.

Using a quantum gas setup consisting of a Bose-Einstein condensate strongly coupled to a high-finesse optical cavity by a transverse pump laser, we experimentally observe an instability of a dissipative continuous time crystal toward a time crystalline state exhibiting two prominent oscillation frequencies. Applying a mean-field approximation model and a Floquet analysis, we theoretically confirm that this transition is a manifestation in a many-body system of a torus bifurcation between a limit cycle (LC) and a limit torus (LT). We theoretically illustrate the LC and LT attractors using the minimal model and experimentally reconstruct them using Takens’ embedding theorem applied to the nondestructively measured intracavity photon dynamics.

We have investigated the transient properties of a ZnO crystal under a pump pulse (pumped crystal) using a pump-probe methodology. By monitoring the second harmonic of the weak probe pulse generated from the pumped crystal, we observe that the angular distribution of the second-harmonic yield becomes asymmetric compared to that without the pump. Importantly, the asymmetry of the second-harmonic generation (SHG) appears to be retarded by nearly 25 fs relative to the pump pulse, and its scaling shows a highly nonlinear dependence on the pump intensity. In addition, by using a two-color pump pulse, we further demonstrate that the asymmetry of SHG is controllable by adjusting the electric field of the two-color pulse. These phenomena can be attributed to the strong-field-induced electric-field-dependent Stark effect. Unlike the conventional intensity-dependent Stark effect, where only energy levels of the pumped target move, electric-field-dependent Stark effect indicates that the excitation induced by the pump pulse can distort the orbital and plays a vital role on the transient property of the pumped crystal. Our work suggests a new freedom for rationally designing the transient property of crystals by controlling the electric field of the pump pulse, which paves the way for realizing petahertz high-speed signal processing.