We report on the measurement of filamented transport of laser-generated fast electron beams in near-critical density plasma. A relativistic intensity long-wave-infrared laser irradiated a hydrodynamically shaped helium gas flow at an electron density $n_e\simeq {10}^{25}{\mathrm{m}}^{-3}$, generating a large flux of fast electrons that propagated beyond the critical surface. The beam-to-background electron density ratio was sufficiently high to drive growth of Weibel-like filamentation, which was measured by optical probing to extend up to $800\mathrm{\mu }\mathrm{m}$ with radii $\sim 10\mathrm{\mu }\mathrm{m}$. Particle-in-cell simulations reproduce the main features of the filamentation generation, suggesting that collisionless processes are dominant in these interactions. Expansion of the filaments after formation infers a fast electron heated plasma temperature $\sim 400\mathrm{eV}$ in the overcritical density plasma.

In the superionic phase of silver iodide, we observe a distorted tetragonal structure characterized by symmetry breaking in the cation distribution. This phase competes with the well known bcc phase with a symmetric cation distribution, at an energetic cost of only a few $\mathrm{meV}/\mathrm{atom}$. The small energy difference suggests that these competing structures may both be thermally accessible near the superionic transition temperature. We also find that the distribution of silver ions depends on the low-temperature parent polymorph, with memory persisting in the superionic phase on the nanosecond timescales accessible in our simulations. Furthermore, simulations on the order of 100 ns reveal that even at temperatures where the bcc phase is stable, significant fluctuations toward the tetragonal lattice structure remain. Our results are consistent with many “anomalous” experimental observations and offer a molecular mechanism for the “memory effect” in silver iodide.

We report on chute measurements of the free-surface velocity $v$ in dense flows of spheres and diverse sands and spheres-sand mixtures down rough inclines. These and previous measurements are inconsistent with standard flow rules, in which the Froude number $v/\sqrt{gh}$ scales linearly with $h/h_s$ or $(\tan \theta /{\mu }_r{)}^{2}h/h_s$, where ${\mu }_r$ is the dynamic friction coefficient, $h$ the flow thickness, and $h_s(\theta )$ its smallest value that permits a steady, uniform dense flow state at a given inclination angle $\theta$. This is because the characteristic length $L$ a flow needs to fully develop can exceed the chute or travel length $l$ and because neither rule is universal for fully developed flows across granular materials. We use a dimensional analysis motivated by a recent unification of sediment transport to derive a flow rule that solves both problems in accordance with our and previous measurements: $v=v_{\infty }[1-\exp (-l/L){]}^{1/2}$, with $v_{\infty }\propto {\mu }_r^{3/2}{[(\tan \theta -{\mu }_r)h]}^{4/3}$ and $L\propto {\mu }_r^3{[(\tan \theta -{\mu }_r)h]}^{5/3}h$.

We present a scalable mixed-species Coulomb crystal clock based on the ${}^1{S}_0\leftrightarrow {{}^{3}P}_0$ transition in ${}^{115}{\mathrm{In}}^{+}$. ${}^{172}{\mathrm{Yb}}^{+}$ ions are cotrapped and used for sympathetic cooling. Reproducible interrogation conditions for mixed-species Coulomb crystals are ensured by a conditional preparation sequence with permutation control. We demonstrate clock operation with a $1{\mathrm{In}}^{+}\text{−}3{\mathrm{Yb}}^{+}$ crystal, achieving a relative systematic uncertainty of $2.5\times {10}^{-18}$ and a relative frequency instability of $1.6\times {10}^{-15}/\sqrt{\tau /1\mathrm{s}}$. We report on absolute frequency measurements with an uncertainty of $1.3\times {10}^{-16}$ and optical frequency comparisons with clocks based on ${}^{171}{\mathrm{Yb}}^{+}$ ($E3$) and ${}^{87}\mathrm{Sr}$. With a fractional uncertainty of $4.4\times {10}^{-18}$, the former is—to our knowledge—the most accurate frequency ratio value reported to date. For the ${}^{115}{\mathrm{In}}^{+}/{}^{87}\mathrm{Sr}$ ratio, we improve upon the best previous measurement by more than an order of magnitude. We also demonstrate operation with four ${}^{115}{\mathrm{In}}^{+}$ clock ions, which reduces the instability to $9.2\times {10}^{-16}/\sqrt{\tau /1\mathrm{s}}$.

We propose a general theory of charge, spin, and orbital diffusion based on Keldysh formalism. Our findings indicate that the diffusivity of orbital angular momentum in metals is much lower than that of spin or charge due to the strong orbital intermixing in crystals. Furthermore, our theory introduces the concept of “spin-orbit polarization” by which a pure orbital (spin) current induces a longitudinal spin (orbital) current, a process as efficient as spin polarization in ferromagnets. Finally, we find that orbital currents undergo momentum swapping, even in the absence of spin-orbit coupling. This theory establishes several key parameters for orbital transport of direct importance to experiments.

Neural criticality has emerged as a unified framework that reconciles diverse multiscale neuronal dynamics such as the irregular firing of individual neurons, sparse synchrony in neuronal populations, and the emergence of scale-free avalanches. However, the functional role of neuronal criticality remains ambiguous. Here, we investigate the neural dynamics and representations in response to external signals in excitation-inhibition balanced networks. We reveal that, in contrast with the case for the traditional critical branching model, the critical state of the balanced network simultaneously achieves maximal response sensitivity, maximal response reliability, and the optimal representation of external signals due to the presence of reliable avalanches induced by external signals. We further demonstrate that heterogeneity in inhibitory connections is a mechanism underlying the reliable critical avalanches and optimal representation. Our study addresses a longstanding challenge concerning the functional significance of neuronal criticality, namely the intricate coexistence of reliability and sensitivity.

We report the discovery of the new isotope ${}^{252}\mathrm{Rf}$. With its extremely short half-life of ${60}_{-30}^{+90}\mathrm{ns}$, it expands the range of half-lives of the known superheavy nuclei by about 2 orders of magnitude. This nucleus was synthesized in its high-$K$ isomeric state, for which we measured a half-life of ${13}_{-3}^{+4}\mathrm{\mu }\mathrm{s}$. Our results confirm a smooth onset of decreasing ground-state spontaneous fission half-lives in the neutron-deficient Rf isotopes toward the isotopic border of ${10}^{-14}\mathrm{s}$, which is the time needed to form an atomic shell. Our findings set a new benchmark for further exploration of phenomena associated with high-$K$ states and inverted fission stability in the heaviest nuclei.

Displacement fields are one of the main tuning knobs employed to engineer flat electronic band dispersions in twisted van der Waals multilayers. Here, we show that electric fields can also be used to tune the phonon dispersion of moiré superlattices formed by noncentrosymmetric materials, focusing on twisted transition metal dichalcogenide homobilayers. This effect arises from the intertwining between the local stacking configuration and the formation of polar domains within the moiré supercell. For small twist angles, increasing the electric field leads to a universal moiré phonon spectrum characterized by a substantially softened longitudinal acoustic phason mode and a flat optical phonon mode, both of which cause a significant enhancement in the vibrational density of states. The phasons also acquire a prominent chiral character, displaying a nonzero angular momentum spread across the Brillouin zone. We discuss how the tunability of the moiré phonon spectra may affect electronic properties, focusing on the recently discovered phenomenon of van der Waals ferroelectricity.

Coupling is an essential mechanism that drives complexity in natural systems, transforming single, noninteracting elements into intricate networks with rich physical properties. Here, we demonstrate a chip-scale coupled laser system that exhibits complex optical states impossible to achieve in an uncoupled system. We show that a pair of coupled semiconductor ring lasers spontaneously forms a frequency comb consisting of the hybridized modes of its coupled cavity, exhibiting a large number of phase-locked tones that anticross with one another. Experimental coherent waveform reconstruction reveals that the hybridized frequency comb manifests itself as pairs of bright and dark picosecond-long solitons circulating simultaneously. The dark and bright solitons exit the coupled cavity at the same time, leading to breathing bright solitons temporally overlapped with their dark soliton counterparts—a state inaccessible for a single, free-running laser. Our results demonstrate that the rules that govern allowable states of light can be broken by simply coupling elements together, paving the way for the design of more complex networks of coupled on-chip lasers.

The planar Hall effect in 3D systems is an effective probe for their Berry curvature, topology, and electronic properties. However, the Berry curvature-induced conventional planar Hall effect is forbidden in 2D systems as the out-of-plane Berry curvature cannot couple to the band velocity of the electrons moving in the 2D plane. Here, we demonstrate a unique 2D planar Hall effect (2DPHE) originating from the hidden planar components of the Berry curvature and orbital magnetic moment in quasi-2D materials. We identify all planar band geometric contributions to 2DPHE and classify their crystalline symmetry restrictions. Using gated bilayer graphene as an example, we show that in addition to capturing the hidden band geometric effects, 2DPHE is also sensitive to the Lifshitz transitions. Our Letter motivates further exploration of hidden planar band geometry-induced 2DPHE and related transport phenomena for innovative applications.

Gradient descent prevails in artificial neural network training, but seems inept for spiking neural networks as small parameter changes can cause sudden, disruptive appearances and disappearances of spikes. Here, we demonstrate exact gradient descent based on continuously changing spiking dynamics. These are generated by neuron models whose spikes vanish and appear at the end of a trial, where it cannot influence subsequent dynamics. This also enables gradient-based spike addition and removal. We illustrate our scheme with various tasks and setups, including recurrent and deep, initially silent networks.

We demonstrate continuous loading and strong collective coupling of atoms to a high finesse ring cavity. A series of spatially separated laser cooling stages delivers a continuous flux of $2.1(3)\times {10}^7$ ${}^{88}\mathrm{Sr}\mathrm{atoms}/\mathrm{s}$ into an intracavity magic wavelength lattice where the atoms are deterministically transported inside the ring cavity. We observe a continuous atom-cavity vacuum Rabi splitting, demonstrating the first steady-state strong collective coupling on a narrow linewidth atomic transition. This Letter opens the path to future continuous cold atom devices, such as a continuous wave superradiant laser with millihertz linewidth and low vibration sensitivity, enabling searches for new physics and technologies.

We present the first results from a dark matter search using six Skipper-CCDs in the SENSEI detector operating at SNOLAB. We employ a bias-mitigation technique of hiding approximately 46% of our total data and aggressively mask images to remove backgrounds. Given a total exposure after masking of 100.72 gram-days from well-performing sensors, we observe 55 two-electron events, 4 three-electron events, and no events containing 4–10 electrons. The two-electron events are consistent with pileup from one-electron events. Among the 4 three-electron events, 2 appear in pixels that are likely impacted by detector defects, although not strongly enough to trigger our “hot-pixel” mask. We use these data to set world-leading constraints on sub-GeV dark matter interacting with electrons and nuclei.

We study the reliability function of general classical-quantum channels, which describes the optimal exponent of the decay of decoding error when the communication rate is below the capacity. As the main result, we prove a lower bound, in terms of the quantum Rényi information in Petz’s form, for the reliability function. This resolves Holevo’s conjecture proposed in 2000, a long-standing open problem in quantum information theory. It turns out that the obtained lower bound matches the upper bound derived by Dalai in 2013, when the communication rate is above a critical value. Thus, we have determined the reliability function in this high-rate case. Our approach relies on Renes’ breakthrough made in 2022, which relates classical-quantum channel coding to that of privacy amplification, as well as our new characterization of the channel Rényi information.

The rapidly increasing computational demands for artificial intelligence (AI) have spurred the exploration of computing principles beyond conventional digital computers. Physical neural networks (PNNs) offer efficient neuromorphic information processing by harnessing the innate computational power of physical processes; however, training their weight parameters is computationally expensive. We propose a training approach for substantially reducing this training cost. Our training approach merges an optimal control method for continuous-time dynamical systems with a biologically plausible training method—direct feedback alignment. In addition to the reduction of training time, this approach achieves robust processing even under measurement errors and noise without requiring detailed system information. The effectiveness was numerically and experimentally verified in an optoelectronic delay system. Our approach significantly extends the range of physical systems practically usable as PNNs.

Understanding the behavior of dense hadronic matter is a central goal in nuclear physics as it governs the nature and dynamics of astrophysical objects such as supernovae and neutron stars. Because of the nonperturbative nature of quantum chromodynamics (QCD), little is known rigorously about hadronic matter in these extreme conditions. Here, lattice QCD calculations are used to compute thermodynamic quantities and the equation of state of QCD over a wide range of isospin chemical potentials with controlled systematic uncertainties. Agreement is seen with chiral perturbation theory when the chemical potential is small. Comparison to perturbative QCD at large chemical potential allows for an estimate of the gap in the superconducting phase, and this quantity is seen to agree with perturbative determinations. Since the partition function for an isospin chemical potential ${\mu }_I$ bounds the partition function for a baryon chemical potential ${\mu }_B=3{\mu }_I/2$, these calculations also provide rigorous nonperturbative QCD bounds on the symmetric nuclear matter equation of state over a wide range of baryon densities for the first time.

The Navier-Stokes equations are paradigmatic equations describing hydrodynamics of an interacting system with microscopic interactions encoded in transport coefficients. In this work we show how the Navier-Stokes equations arise from the microscopic dynamics of nearly integrable 1D quantum many-body systems. We build upon the recently developed hydrodynamics of integrable models to study the effective Boltzmann equation with collision integral taking into account the non-integrable interactions. We compute the transport coefficients and find that the resulting Navier-Stokes equations have two regimes, which differ in the viscous properties of the fluid. We illustrate the method by computing the transport coefficients for an experimentally relevant case of coupled 1D cold-atomic gases.

Smectic liquid crystals can be viewed as model systems for lamellar structures for which there has been extensive theoretical development. We demonstrate that a nonlinear energy description is required with respect to the usual Landau–de Gennes elasticity in order to explain the observed layer spacing of highly curved smectic layers. Using x-ray diffraction we have quantitatively determined the dilation of bent layers distorted by antagonistic anchoring (as high as 1.8% of dilation for the most bent smectic layers) and accurately described it by the minimal nonlinear expression for energy. We observe a 1° tilt of planar layers that are connected to the curved layers. This value is consistent with simple energetic calculations, demonstrating how the bending energy impacts the overall structure of a thin distorted smectic film. Finally, we show that combined x-ray measurements and theoretical modeling allow for the quantitative determination of the number of curved smectic layers and of the resulting thickness of the dilated region with unprecedented precision.

We explore experimentally how a conical surface frustrates the growth of colloidal crystals. Whereas crystals on a cylinder can form perfect commensurate bands, crystals on a cone tend to form tilt grain boundaries with misorientation angles set by the conical geometry. However, at small cone angles, where the surface deviates only slightly from that of a cylinder, crystals can form commensurate bands, the widths limited by the emergence of dislocations. The dislocations allow the crystal to continue growing beyond the limiting width. We relate these effects to the gradient in circumference on a cone, a consequence of the Gaussian curvature localized at the apex.

The Super-Kamiokande and T2K Collaborations present a joint measurement of neutrino oscillation parameters from their atmospheric and beam neutrino data. It uses a common interaction model for events overlapping in neutrino energy and correlated detector systematic uncertainties between the two datasets, which are found to be compatible. Using 3244.4 days of atmospheric data and a beam exposure of $19.7(16.3)\times {10}^{20}$ protons on target in (anti)neutrino mode, the analysis finds a $1.9\sigma$ exclusion of $CP$ conservation (defined as $J_{CP}=0$) and a $1.2\sigma$ exclusion of the inverted mass ordering.