The acceleration of electrons by surface plasma waves (SPWs) generated during the interaction of ultrashort, linearly polarized, and contrast-enhanced laser pulses at a peak intensity of $\sim 6\times {10}^{20}{\mathrm{W}\mathrm{cm}}^{-2}$ with flat, noncorrugated foils at parallel incidence (with respect to the target surface) is investigated. We experimentally demonstrate the generation of a collimated electron beam ($<0.6\mathrm{mrad}$) with a non-Maxwellian spectrum, characterized by peaks at superponderomotive energies (30–36 MeV) and total charge $\sim 120\mathrm{pC}$. Through particle-in-cell (PIC) simulations, we identify the $\mathbf{J}\times \mathbf{B}$ force at the front edge as the primary mechanism for injecting electrons into the SPW, where they are further accelerated. Furthermore, our simulation findings reveal that lateral surface contaminants influence SPW dynamics and give rise to a long-ranging plasmonic mode.

Accurately quantifying the energy loss rate of proton beams in liquid water is crucial for the precise application and improvement of proton therapy, whereas the slowing down of protons in water ices also plays an important role in astrophysics. However, precisely determining the electronic stopping power, particularly for the liquid phase, has been elusive so far. Experimental techniques are difficult to apply to volatile liquids, and the availability of sufficient reliable measurements has been limited to the solid and vapor phases. The accuracy of current models is typically limited to proton energies just above the energy loss maximum, making it difficult to predict radiation effects at an energy range of special relevance. We elucidate the phase differences in proton energy loss in water in a wide energy range ($0.001-10\mathrm{MeV}$) by means of real-time time-dependent density functional theory combined with the Penn method. This nonperturbative model, more computationally efficient than current approaches, describes the phase effects in water in excellent agreement with available experimental data, revealing clear deviations around the maximum of the stopping power curve and below. As an important outcome, our calculations reveal that proton stopping quantities of liquid water and amorphous ice are identical, in agreement with recent similar observations for low-energy electrons, pointing out this equivalence for all charged particles. This could help to overcome the limitation in obtaining reliable experimental information for the biologically relevant liquid water target.

We explore the potential of using late-time galaxy spins to test the parity symmetry of primordial vector fossils. Using $N$-body simulations, we analyze halo spins as a reliable proxy for galaxy spins to investigate the detectability of this effect. We develop a novel approach to generate initial conditions (ICs) that have substantial parity asymmetry but do not alter the initial matter power spectrum. We construct the initial spin fields from the parity broken ICs and halo spin fields using late-time halos evolved from such ICs. Focusing on the helicity of these vector fields, we detect substantial asymmetry in the initial spin field. In addition, we find that over 50% of the initial spin field’s asymmetry remains in the late-time halo spin field on a range of scales. Based on mock galaxy spin fields derived from the halo spin fields, we forecast that a maximum detection at $13\sigma$ is possible with the final DESI BGS for the model considered in this analysis. Our findings demonstrate that primordial vectorial parity violation survives nonlinear gravitational evolution, and thus, can be effectively probed with galaxy spins at late times.

Kelvin probe force microscopy (KPFM) is widely used in stationary and dynamic studies of contact electrification. An obvious question that connects these two has been overlooked: when are charge dynamics too fast for stationary studies to be meaningful? Using a rapid transfer system to quickly perform KPFM after contact, we find the dynamics are too fast in all but the best insulators. Our data further suggest that dynamics are caused by bulk as opposed to surface conductivity, and that charge-transfer heterogeneity is less prevalent than previously suggested.

The determination of the absolute neutrino mass scale remains a fundamental open question in particle physics, with profound implications for both the standard model and cosmology. Direct kinematic measurements, independent of model-dependent assumptions, provide the most robust approach to address this challenge. Here we present the most stringent upper bound on the effective electron neutrino mass ever obtained with a calorimetric measurement of the electron capture decay of ${}^{163}\mathrm{Ho}$. The HOLMES experiment employs an array of ion-implanted transition-edge sensor (TES) microcalorimeters, achieving an average energy resolution of 6 eV FWHM with a scalable, multiplexed readout technique. With a total of $7\times {10}^7$ decay events recorded over two months and a Bayesian statistical analysis, we derive an upper limit of $m_{\beta }<27\mathrm{eV}/c^2$ at 90% credibility. These results validate the feasibility of ${}^{163}\mathrm{Ho}$ calorimetry for next-generation neutrino mass experiments and demonstrate the potential of a scalable TES-based microcalorimetric technique to push the sensitivity of direct neutrino mass measurements beyond the current state of the art.

We report precision measurements on cumulants ($C_n$) and factorial cumulants (${\kappa }_n$) of (net) proton number distributions up to fourth order in $\mathrm{Au}+\mathrm{Au}$ collisions over center-of-mass energies $\sqrt{s_{NN}}=7.7–27\mathrm{GeV}$ from phase II of the Beam Energy Scan program at RHIC. (Anti)protons are selected at midrapidity ($|y|<0.5$) within a transverse momentum range of $0.4<p_T<2.0\mathrm{GeV}/c$. Relative to various noncritical-point model calculations and peripheral collision 70%–80% data, the net proton $C_4/C_2$ measurement in 0%–5% collisions shows a minimum around 19.6 GeV for significance of deviation at $\sim 2–5\sigma$. A minimum in $C_4/C_2$ with respect to a noncritical baseline is expected to be a characteristic feature of the signature associated with a critical point in the QCD phase diagram. In addition, deviations from noncritical baselines around the same collision energy region are also seen in proton factorial cumulant ratios, especially in ${\kappa }_2/{\kappa }_1$ and ${\kappa }_3/{\kappa }_1$. Dynamical model calculations including a critical point are called for in order to understand these precision measurements.

We present a response-augmented machine-learning (ML) approach to the energetics of electrified metal surfaces. We leverage local descriptors to learn the work function as the first-order energy change to introduced bias charges and stabilize this learning through Born effective charges. This permits the efficient extension of ML interatomic potential architectures to include finite bias effects up to second order. Application to OH at Cu(100) rationalizes the experimentally observed $p\mathrm{H}$ dependence of the preferred adsorption site in terms of a non-Nernstian charge-induced site switching.

Graphene-based moiré superlattices provide a versatile platform for exploring novel correlated and topological electronic states, driven by enhanced Coulomb interactions within flat bands. The intrinsic tunability of graphene’s multiple degrees of freedom enables precise control over these complex quantum phases. In this study, we observe a range of competing phases and their transitions in rhombohedral stacked hexalayer graphene on hexagonal boron nitride ($r\text{−}6\mathrm{G}/\mathrm{hBN}$) moiré superlattices. When electrons are polarized away from the moiré superlattice, we first identify a Chern insulator with reversible Chern numbers at $v=1$ (one electron per moiré cell), revealing a competition between bulk and edge orbital magnetization. At $v=2$, three distinct insulating phases—spin-antiferromagnetic, spin-polarized, and valley-polarized—emerge under vertical displacement field $D$ and magnetic field $B_{\perp }$, governed by hierarchical isospin symmetry breaking. Furthermore, charge density wave (CDW) states at $\nu =1/3$ and $2/3$, along with a magnetic-field-induced stripe phase at $\nu =1/2$, demonstrate tunable correlated orders at fractional fillings. Our findings reveal a rich interplay of charge, isospin, topology, and magnetic field in rhombohedral graphene moiré superlattices.

Entanglement is the cornerstone of quantum communication, yet conventional detection relies solely on local measurements. In this Letter, we present an experimental demonstration, based on an improved theoretical framework showing that one-way local operations and classical communication (1-LOCC) can significantly outperform purely local measurements in detecting quantum entanglement. By casting the entanglement detection problem as a semidefinite program, we derive protocols that minimize false negatives at fixed false-positive rates. A variational generative machine-learning algorithm efficiently searches over high-dimensional parameter spaces, identifying states and measurement strategies that exhibit a clear 1-LOCC advantage. Experimentally, we realize a genuine event-ready protocol on a three-dimensional photonic entanglement source, employing fiber delays as short-lived quantum memories. We implement rapid, field-programmable gate array-based sampling of the optimized probabilistic instructions, allowing Bob’s measurement settings to adapt to Alice’s outcomes in real time. Our results validate the predicted 1-LOCC advantage in a realistic noisy setting and reduce the experimental trials needed to certify entanglement. These findings mark a step toward scalable, adaptive entanglement detection methods crucial for quantum networks and computing, paving the way for more efficient generation and verification of high-dimensional entangled states.

We present a theory for the relaxation time of the octupole order parameter in nanoscale chiral antiferromagnets (AFMs) coupled to thermal baths and spin injection sources. Using stochastic spin dynamics simulations, we demonstrate that the octupole moment relaxes through two distinct mechanisms—escape over a barrier and precessional dephasing—as the barrier for octupole fluctuations is lowered relative to the thermal energy. Notably, the octupole moment relaxes orders of magnitude faster than the typical dipolar order parameters, reaching picosecond timescales. By combining Langer’s theory with an effective low-energy description of octupole dynamics in chiral AFMs, we derive analytical expressions for the relaxation times. We find that relaxation in chiral AFMs parallels dipole relaxation in $XY$ magnets, with exchange fields serving the role of the dipole fields. Further, by drawing on the analogy between order parameter dynamics in $XY$ magnets under spin injection and current-biased Josephson junctions, we propose a new scheme for electrically tuning the octupole relaxation times. Our Letter offers fundamental insights for the development of next-generation spintronic devices that harness octupole order parameters for information encoding.

In dense colloids and simulated glasses, it has been discovered that plastic particle rearrangements correlate with nonphononic low-frequency vibrational modes. Here, we demonstrate that this correlation also holds for a very different material class of complex plasmas under shear, characterized by long-range interactions and nonreciprocal forces. We perform experiments with a deformed amorphous quasi-two-dimensional binary complex plasma under optical pressure, which gives rise to a controlled shear rate, and confirm our findings with extensive particle-resolved computer simulations.

Bulk-boundary correspondence is the foundational principle of topological physics, first established in the quantum Hall effect, where a $D$-dimensional topologically nontrivial bulk gives rise to ($D-1$)-dimensional boundary states. The advent of higher-order topology has generalized this principle to a hierarchical chain, enabling topological states to appear at ($D-2$) or even lower-dimensional boundaries. To date, all known realizations of topological systems must require a topologically nontrivial bulk to initiate the chain of action for bulk-boundary correspondence. Here, in an acoustic crystal platform, we experimentally demonstrate an exception to this paradigm—embedded topology in a trivial bulk—where the bulk-boundary correspondence originates from a trivial bulk. Rather than relying on global symmetries, we employ projective crystal symmetry, which induces nontrivial topology not at the outset in the $D$-dimensional bulk, but midway through the correspondence hierarchy in lower-dimensional boundaries. We further realize a three-dimensional system exhibiting embedded topology that supports zero-dimensional topological states, achieving the longest possible chain of action for such an unconventional bulk-boundary correspondence in physical space. Our Letter experimentally establishes a new form of bulk-boundary correspondence initiated from a trivial bulk, opening additional degrees of freedom for the design of robust topological devices.

In the last decade, the first law of binary black hole mechanics played an important unifying role in the gravitational two-body problem. More recently, binary black hole scattering and the application of high-energy physics methods have provided a new avenue into this classical problem. In this Letter, we connect these two themes by extending the first law to the case of scattering orbits. We present derivations based on classical S-matrix, Hamiltonian, and pseudo-Hamiltonian methods, the last of which allows us to include dissipative effects for the first time. Finally, a “boundary to bound” map links this first law to the traditional bound-orbit version. Through this map a little-known observable for scatter orbits, the elapsed proper time, is mapped to the Detweiler redshift for bound orbits, which is an invariant building block in gravitational waveform models.

We show that idealized Dicke superradiant decay from a fully inverted state can at all times be described by a positive statistical mixture of coherent spin states (CSS). Since CSS are separable, this implies that no entanglement is involved in Dicke decay. Based on this result, we introduce a new numerical quantum trajectory approach leading to low-entanglement unravelings. This opens up new possibilities for employing matrix product state (MPS) techniques for large-scale numerical simulations with collective decay processes.

Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between the two dark matter particles ${\chi }_1$ and ${\chi }_2$, with $m({\chi }_2)>m({\chi }_1)$, is induced by a dark Higgs field and a corresponding dark Higgs boson $h^{\prime }$. We present a search for dark matter in events with two vertices, at least one of which must be displaced from the interaction region, and missing energy. Using a $365{\mathrm{fb}}^{-1}$ data sample collected at Belle II, which operates at the SuperKEKB $e^{+}{e}^{-}$ collider, we observe no evidence for a signal. We set upper limits on the product of the production cross section $\sigma (e^{+}{e}^{-}\to h^{\prime }{\chi }_1{\chi }_2)$, and the product of branching fractions $\mathcal{B}({\chi }_2\to {\chi }_1{e}^{+}{e}^{-})\times \mathcal{B}(h^{\prime }\to x^{+}{x}^{-})$, where $x^{+}{x}^{-}$ indicates ${\mu }^{+}{\mu }^{-},{\pi }^{+}{\pi }^{-}$, or $K^{+}{K}^{-}$, as functions of $h^{\prime }$ mass and lifetime at the level of ${10}^{-1}\mathrm{fb}$. We set model-dependent upper limits on the dark Higgs mixing angle at the level of ${10}^{-5}$ and on the dark photon kinetic mixing parameter at the level of ${10}^{-3}$. This is the first search for dark Higgs bosons in association with inelastic dark matter.

Over the last few decades, the predominant strategies for controlling spontaneous emission have involved tailoring the spatial surroundings of quantum emitters or atoms to create resonant or spatially periodic photonic structures. However, the rise of time-varying photonics has prompted a reevaluation of spontaneous emission in dynamically changing environments, especially within photonic time crystals, where optical properties undergo time-periodic modulation. Here, we apply classical light-matter interaction theory together with Floquet analysis to reveal a substantial enhancement of the spontaneous emission decay rate at the momentum gap frequency in photonic time crystals. Moreover, our findings suggest that photonic time crystals enable a nonequilibrium light-matter interaction process: the spontaneous excitation of an atom from its ground state to an excited state, accompanied by the concurrent emission of a photon, referred to as spontaneous emission excitation.

Experimental and numerical studies of incompressible turbulence suggest that the mean dissipation rate of kinetic energy remains constant as the Reynolds number tends to infinity (or the nondimensional viscosity tends to zero). This anomalous behavior is central to many theories of high-Reynolds-number turbulence and has been termed the “zeroth law” for this reason. Here, we report a sequence of direct numerical simulations of incompressible Navier-Stokes in a box with periodic boundary conditions, which indicate the likelihood that the anomaly vanishes at a rate that agrees with the scaling of third moment of absolute velocity increments. Our results suggest that turbulence without solid boundaries or walls may not develop strong enough singularities to sustain the strict version of the zeroth law.

A novel approach designed to directly estimate microcanonical quantities from energy histograms is proposed, which enables the immediate systematic identification and classification of phase transitions in physical systems of any size by means of the recently introduced generalized microcanonical inflection-point analysis method. The application to the aggregation problem of GNNQQNY heptapeptides, for which the entire transition sequence is revealed, shows the power of this promising method.

We present the ultra-low-temperature thermal conductivity measurements on single crystals of the transition-metal dichalcogenide material $4{\mathrm{Hb}\text{−}\mathrm{TaS}}_2$, which has recently been proposed as a topological superconductor candidate. In zero field, a small residual linear term ${\kappa }_0/T$ is observed, indicating the existence of a residual density of states in the superconducting state. The slow field dependence of ${\kappa }_0/T$ at low fields rules out the presence of nodes in the superconducting gap, and the S-shaped field dependence across the full field range suggests multiple superconducting gaps in $4{\mathrm{Hb}\text{−}\mathrm{TaS}}_2$. Our results provide evidence for multiband gapless superconductivity in $4{\mathrm{Hb}\text{−}\mathrm{TaS}}_2$, and the residual density of states come from certain gapless Fermi surfaces.

The KM3NeT Collaboration recently announced the detection of a neutrino with energy 220 PeV. One possible source of such ultrahigh-energy particles is the rapid emission of energetic Hawking radiation from a primordial black hole (PBH) near the end of its evaporation lifetime. The mass distribution for PBHs features a power-law tail for small masses; a small subset of PBHs would be undergoing late-stage evaporation today. We find that recent high-energy neutrino events detected by the IceCube and KM3NeT Collaborations, with energies $\mathcal{O}(1-{10}^2)\mathrm{PeV}$, are consistent with event-rate expectations if a significant fraction of the dark matter consists of PBHs.