The task of experimentally investigating the inherently dual properties of a supersolid, a simultaneous superfluid and solid, has become more critical following the recent experimental exploration of supersolid regimes in dipolar Bose-Einstein condensates (BECs) of ${}^{164}\mathrm{Dy}$. We introduce a supersolid order parameter that uses vortex-vortex trajectory correlations to simultaneously reveal the periodic density of the underlying solid and superfluidity in a single measure. We propose experiments using existing technology to optically create and image trajectories of vortex dipoles in dipolar BECs that is applicable to large system sizes. We numerically test our observable and find that vortex-vortex correlations reveal the supersolid lattice structure while distinguishing it from superfluidity even in the presence of dissipation. Our method sets the stage for experiments to use vortex trajectory correlations to investigate fundamental properties of supersolids arising from their dynamics and phase transitions as experimental system sizes are increased.

An incident wave at a temporal interface, created by an abrupt change in system parameters, generates time-refracted and time-reflected waves. We find topological characteristics associated with the temporal interface that separates distinct spatial topologies and report a novel bulk-boundary correspondence for the temporal interface. The vanishing of either time refraction or time reflection records a topological phase transition across the temporal interface, and the difference of bulk band topology predicts nontrivial braiding hidden in the time refraction and time reflection coefficients. These findings, which are insensitive to spatial boundary conditions and robust against disorder, are demonstrated in a synthetic frequency lattice with rich topological phases engendered by long-range couplings. Our work reveals the topological aspect of temporal interface and paves the way for using the time boundary effect to probe topological phase transitions and topological invariants.

Since the pioneering works of Landau and Feynman, the origin of a roton minimum in the excitation spectrum of a quantum Bose liquid has been debated. A consensus has been reached on relation of the roton to eventual solidification, but this viewpoint still remains to be connected to the polaronic concept of an impurity pushing through a dense medium. The diagrammatic theory allows one to approach the problem qualitatively from a dilute limit. We revisit the equation for the elementary excitation spectrum obtained in the ladder approximation and argue that polaronic renormalization of the quasiparticle mass has a contribution due to matter-wave refraction. At low energies attenuation of the quasiparticle wave turns out to be dramatically suppressed by the condensate. Refractive correction to the mass is enhanced by Bose statistics at high momenta and produces autolocalization of an elementary excitation upon increasing the density.

Charged domain walls (CDWs) in ferroelectrics are often characterized as excited states, even after full bound charge compensation at domain walls (DWs). Here, we propose a mechanism where negative gradient energy ($E_{\mathrm{grad}}$) counteracts the large positive electrostatic energy ($E_{\mathrm{el}}$) induced by bound charge at DWs, stabilizing the CDWs over the bulk state, even with partial or no bound charge compensation. As proof of scheme, we demonstrate that negative $E_{\mathrm{grad}}$ of modes, which reverse their sign during the formation of CDWs in ${\mathrm{HfO}}_2$, partially offsets $E_{\mathrm{el}}$. Their corresponding remaining $E_{\mathrm{el}}$ can be neutralized by partial bound charge compensation. Exceeding this partial compensation, achieved through the substitution of ${\mathrm{Nb}}^{5+}$ at tail-to-tail and ${\mathrm{Y}}^{3+}$ at head-to-head DWs for ${\mathrm{Hf}}^{4+}$, CDWs exhibit unprecedented stability over the bulk state. The 1.33 eV band gap of the most stable CDW is particularly suitable for photovoltaic applications due to their potential for efficient electron-hole separation. We further reveal that negative phonon band curvatures are useful descriptors to uncover the origin of negative $E_{\mathrm{grad}}$ in such CDWs, which can be estimated simply by phonon band fitting, making our scheme easy to implement for realizing CDWs beyond ${\mathrm{HfO}}_2$.

Ultrastrong nanotwinned (NT) metals hold promise for mitigating friction and wear—essential for enhancing the energy efficiency and longevity of all moving systems. However, optimizing their tribological performance has long suffered from the absence of friction and wear laws across varying tribological loading scales. Here, we have discovered full-scaling twin lamella spacing ($\lambda$)-dependent friction and wear laws in NT pure nickel and identified critical deformation mechanisms for reducing friction and wear. Nanoscale friction initially increases with decreasing $\lambda$, peaking at 20 nm, and then decreases due to a transition from dislocation-twin boundary interactions to detwinning. Under microscale loading, friction and wear reduce linearly with decreasing $\lambda$, attributed to an unforeseen phase transition from face-centered cubic to hexagonal close-packed structures. Furthermore, under macroscale loading, the formation of a durable oxide layer and a stable gradient nanostructure in nanotwinned nickel with $\lambda$ exceeding 20 nm aids in mitigating wear loss.

We report measurements of the mean settling velocities for suspensions of discs and rods in the Stokes regime for a number of particle aspect ratios. All these shapes display “hindered settling,” namely, a decrease in settling speed as the solid volume fraction is increased. A comparison of our data to spheres reveals that discs and rods show less hindering than spheres at the same relative interparticle separation. The data for all six of our particle shapes may be scaled to collapse on that of spheres, with a scaling factor that depends only on the volume of the particle relative to a sphere. Despite the orientational degrees of freedom available with nonspherical particles, it thus appears that the dominant contribution to the hindered settling emerges from terms that are simply proportional to the volume of the sedimenting particles, enabling prediction of hindered settling of other nonpolar axisymmetric shapes.

Shadow estimation is a sample-efficient protocol for learning the properties of a quantum system using randomized measurements, but the current understanding of qudit shadow estimation is quite limited compared with the qubit setting. Here, we clarify the sample complexity of qudit shadow estimation based on the Clifford group, where the local dimension $d$ is an odd prime. Notably, we show that the overhead of qudit shadow estimation over the qubit counterpart is only $\mathcal{O}(d)$, which is independent of the qudit number $n$, although the set of stabilizer states may deviate exponentially from a 3-design with respect to the third moment operator. Furthermore, by adding one layer of magic gates, we propose a simple circuit that can significantly boost the efficiency. Actually, a single magic gate can already eliminate the $\mathcal{O}(d)$ overhead in qudit shadow estimation and bridge the gap from the qubit setting.

A targeted experiment at the National Ignition Facility (NIF) confirms the presence of multispecies hydrodynamics in inertial confinement fusion hohlraums relevant to ignition. The effects are identified by filling the gold hohlraum with a deuterium-tritium (DT) gas mixture instead of helium. As the hohlraum is heated by the NIF lasers, it implodes inward, compressing and heating the DT, which leads to fusion. The resulting DT-fusion neutrons are measured in space, time, yield, angle, and energy. A distinct, peaked, triangular shape in the radial neutron emission profile provides evidence of a “leaky piston” effect caused by the interpenetration of DT into the expanding gold. This process reduces the reversibility of DT compression and decreases neutron generation on the temporal trailing edge compared to the leading edge. These results are well described by multispecies hydrodynamics simulations, which reproduce the observed spatial and temporal features, as well as the total neutron yield and angularly resolved energy spectra. In contrast, conventional simulations that use only single-species physics fail to match the experimental data. They overpredict the neutron yield, produce a flatter-than-observed spatial profile, and show excessive emission at late times compared to the experimental measurements.

Using space-time-resolved Thomson scattering, we investigate experimentally the development of electrostatic waves in a preformed undercritical helium plasma driven by a $1.059\mathrm{\mu }\mathrm{m}$ laser pulse of $\sim 1.5\mathrm{ps}$ duration and $\sim {10}^{15–16}\mathrm{W}{\mathrm{cm}}^{-2}$ mean intensity. We observe the excitation of intense ion plasma waves (IAWs) over a broad wave number range, distinct from what is expected from stimulated Brillouin scattering or Langmuir decay instability. These IAWs are correlated with the occurrence of backward stimulated Raman scattering (B-SRS) at earlier times but persist much longer than the B-SRS-driven electron plasma waves. Particle-in-cell modeling reveals that they result from an ion acoustic instability triggered by the bulk electrons drifting against the ions to neutralize the current carried by the B-SRS-generated hot electrons. The properties of the simulated unstable IAWs match well with the measurements.

The Kuramoto model and its generalizations are universal models of collective behavior in oscillatory networks. We provide conditions on the coupling function such that the Kuramoto system with four globally coupled identical oscillators has chaotic attractors: a pair of Lorenz attractors or a four-winged analog of the Lorenz attractor. The attractors emerge near the triple instability threshold of the splay-phase synchronization state of the oscillators. We provide theoretical arguments and verify numerically, based on the pseudohyperbolicity test, that the chaotic dynamics are robust with respect to small, e.g., time-dependent, perturbations of the system. The robust chaoticity should also be inherited by any network of weakly interacting systems with such attractors.

The effective viscosity of liquid foams is controlled by Marangoni forces and therefore by the transport of surfactants. Direct tracking of the latter during foam deformation is out of reach. Besides, the competition between diffusion and convection on the interfaces and in the bulk of complex assemblies of thin films and menisci is still an open problem. These shortcomings severely limit our understanding of foam rheology and stability. In this Letter, we use a comprehensive characterization of in-plane flows in an elementary foam during imposed deformation to determine indirectly the flux of surfactants from a film to its first neighbor. We show that the meniscus connecting the films, despite its potential role as a surfactant reservoir, is not involved in surfactant transport. This information has been identified as a key missing piece in local foam viscosity models of the literature.

Investigating causation in the quantum domain is crucial. Despite numerous studies of correlations in quantum many-body systems, causation, which is very distinct from correlations, has hardly been studied. We address this by demonstrating the efficacy of the newly established causation measure, quantum Liang information flow, in quantifying causality across phase diagrams of quantum many-body systems. We focus on quantum criticality, which are highly nonclassical points. We extract causation behavior across a spectrum-wide critical point and a ground state second-order phase transition in both integrable and nonintegrable systems. Across criticality, each case exhibits distinct hallmarks, different from correlation measures. We also deduce that quantum causation qualitatively follows the quasiparticle picture of information propagation in integrable systems but exhibits enhanced quantum nonlocality near criticality. At times significantly larger than the spatial separation, it extracts additional features from the equilibrium wave function, leading to a peak just before the critical point for near boundary sites.

Spontaneous symmetry breaking (SSB) is crucial to the occurrence of phase transitions. Once a phase transition occurs, a quantum system presents degenerate eigenstates that lack the symmetry of the Hamiltonian. After crossing the critical point, the system is essentially evolved to a quantum superposition of these eigenstates until decoherence sets in. Despite the fundamental importance and potential applications in quantum technologies, such quantum-mechanical SSB phenomena have not been experimentally explored in many-body systems. We here present an experimental demonstration of the SSB process in the Lipkin-Meshkov-Glick model, governed by the competition between the individual driving and intraqubit interaction. The model is realized in a circuit quantum electrodynamics system, where 6 Xmon qubits are coupled in an all-to-all manner through virtual photon exchange mediated by a resonator. The observed nonclassical correlations among these qubits in the symmetry-breaking region go beyond the conventional description of SSB, shedding new light on phase transitions for quantum many-body systems.

The cosmic velocity field is an unbiased probe of the total matter distribution but is challenging to measure directly at intermediate and high redshifts. The large-scale velocity field imprints a signal in the cosmic microwave background (CMB) through the kinetic Sunyaev-Zeldovich (kSZ) effect. We perform the first 3D reconstruction of the large-scale velocity field from the kSZ effect by applying a quadratic estimator to CMB temperature maps and the 3D positions of galaxies. We do so by combining CMB data from the fifth data release of the Atacama Cosmology Telescope (in combination with Planck) and a spectroscopic galaxy sample from the Sloan Digital Sky Survey. We then measure the galaxy-velocity cross-power spectrum and detect the presence of the kSZ signal at a signal-to-noise ratio of $7.2\sigma$. Using this galaxy-velocity cross-correlation alone, we constrain the amplitude of local primordial non-Gaussianity finding $f_{\mathrm{NL}}=-90_{-350}^{+210}$. This pathfinder measurement sets the stage for joint galaxy-CMB kSZ constraints to significantly enhance the $f_{\mathrm{NL}}$ information obtained from galaxy surveys through sample variance cancellation.

We report the first result from a dark photon dark matter search in the mass range from 78.62 to $83.95\mathrm{\mu }\mathrm{eV}/c^2$ with a dielectric haloscope prototype for madmax (Magnetized Disc and Mirror Axion eXperiment). Putative dark photons would convert to detectable photons within a stack consisting of three sapphire disks and a mirror. The emitted power of this system is received by an antenna and successively digitized using a low-noise receiver. No significant signal attributable to dark photons has been observed above the expected background. Assuming unpolarized dark photon dark matter with a local density of ${\rho }_{\chi }=0.3\mathrm{G}\mathrm{eV}{\mathrm{cm}}^3$ we exclude a dark photon to photon mixing parameter $\chi >2.7\times {10}^{-12}$ over the full mass range and $\chi >1.1\times {10}^{-13}$ at a mass of $80.57\mathrm{\mu }\mathrm{eV}/c^2$ with a 95% confidence level. This is the first physics result from a madmax prototype and exceeds previous constraints on $\chi$ in this mass range by up to almost three orders of magnitude.

We show that TeV neutrinos and high-energy gamma rays detected from the nearby active galaxy NGC 1068 can simultaneously be explained in a model based on the beta decays of neutrons produced in the photodisintegration of ${}^4\mathrm{He}$ nuclei on ultraviolet photons in the jet. The photodisintegration of nuclei occurs at energies above several PeV, which explains the 1–100 TeV energies of the observed neutrinos. The TeV gamma-ray flux accompanying the beta decays is expected to be much lower than the neutrino flux, which agrees with the observations of NGC 1068 showing a gamma-ray deficit as compared to the expectations from proton-photon interactions. Furthermore, the synchrotron and inverse Compton gamma-ray flux associated with protons’ Bethe-Heitler pair production and the photopion processes in the jet can be consistent with the observed gamma-ray flux at GeV energies for a plausible range of magnetic fields of jets. This scenario, combining beta decay and Bethe-Heitler, can be applied to other jet Seyfert galaxies such as NGC 4151. Future measurements of the neutrino flavor ratio can help confirm the beta-decay origin of the observed neutrinos.

We report the first rotationally resolved spectrum of a single polyatomic molecular ion in the gas phase. Building upon the recently developed inelastic recoil spectroscopy technique, we have increased spectral resolution by a factor $\sim 10000$; sufficient to observe resolved rotational-vibrational transitions of a single, trapped cyclopropenyl cation (${\mathrm{c}\text{−}\mathrm{C}}_3{\mathrm{H}}_3^{+}$). The precision and sensitivity of IRS shown in this work presents an attractive platform for astrochemistry, single molecule chiral detection, and tests of fundamental physics.

We calculate the exact spectral function of a single impurity repulsively interacting with a bath of fermions in one-dimensional lattices, by deriving the explicit expression of the form factor for both regular Bethe states and the irregular spin-flip state and $\eta$-pairing state, based on the exactly solvable one-dimensional Hubbard model. While at low impurity momentum $Q\sim 0$ the spectral function is dominated by two power-law Fermi singularities, at large momentum we observe that the two singularities develop into two-sided distributions and eventually become anomalous Fermi singularities at the boundary of the Brillouin zone (i.e., $Q=\pm \pi$), with the power-law tails extending toward low energy. Near the quarter filling of the Fermi bath, we also find two broad polaron peaks at large impurity momentum, collectively contributed by many excited many-body states with non-negligible form factors. Our exact results of those distinct features in one-dimensional Fermi polarons, which have no correspondences in two and three dimensions, could be readily probed in cold-atom laboratories by trapping highly imbalanced two-component fermionic atoms into one-dimensional optical lattices.

Radiation-pressure interactions between harmonic oscillators have enabled exquisite measurement precision and control, made possible by using strong sideband drives, enhancing the coupling rate while also linearizing the interaction. In this Letter, we demonstrate a strong intrinsic longitudinal coupling, a circuit quantum electrodynamics analog of the radiation-pressure interaction, between a transmon qubit and a linear microwave resonator. A red-detuned sideband drive results in an on-demand Jaynes-Cummings interaction with a high on-off ratio. We measure a longitudinal coupling rate an order of magnitude larger than all decay rates, placing the device in the strong coupling regime. The intrinsic longitudinal interaction demonstrated here will enable the development of high-connectivity quantum information processing hardware and the exploration of the gravitational decoherence of quantum objects.