We report the precise energy scan measurement of the cross section line shape of $\psi (2S)\to K^{+}{K}^{-}$. The analysis is based on $e^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of $495{\mathrm{pb}}^{-1}$ collected with the BESIII detector at BEPCII. By analyzing the cross section line shape, we extract the relative phase $\mathrm{\Phi }$ between the strong and electromagnetic amplitudes of the $\psi (2S)$ resonance, a fundamental parameter in charmonium physics, based on the assumption that the relative phase between the electromagnetic amplitude of the $\psi (2S)$ resonance and the continuum is zero. Two distinct solutions for the branching fraction $\mathcal{B}$ of $\psi (2S)\to K^{+}{K}^{-}$ are observed: a constructive interference solution with $\mathcal{B}=(7.49\pm 0.41)\times {10}^{-5}$ and $\mathrm{\Phi }=(110.1\pm 6.7)°$, and a destructive interference solution with $\mathcal{B}=(10.94\pm 0.48)\times {10}^{-5}$ and $\mathrm{\Phi }=(-106.8\pm 5.7)°$. A significant correlation between $\mathrm{\Phi }$ and $\mathcal{B}$ is established, demonstrating that interference effects must be taken into account in the $\psi (2S)$ branching fraction measurements. Additionally, the first results for both the $\psi (2S)$ strong form factor, which characterizes the strong coupling between $\psi (2S)$ and $K^{+}{K}^{-}$, and the energy-dependent electromagnetic form factor of the charged kaon in this energy region are reported.

We investigate the QCD transverse-energy ($E_T$) flow distribution within an azimuthal region of phase space, defined by an angular interval $\mathrm{\Delta }\varphi$ on the plane transverse to a chosen reference axis. Vetoes on the resulting $E_T$ are widely employed at the LHC to isolate missing transverse momentum in final states with invisible particles. We show that this observable has logarithmic structures never seen before in QCD calculations. Notably, its description involves the resummation of nonglobal and coherence-violating logarithmic contributions that are more singular than any reported to date. We analyze its all-orders behavior, providing analytical resummation for $pp$ collisions at next-to-double-logarithmic accuracy and numerical resummation at leading-logarithmic accuracy in the Veneziano limit. We further present a computation of the leading coherence-violating correction, highlighting its novel structure. The intricate structure of vetoes in azimuthal gaps reveals new aspects of QCD dynamics and offers a novel probe of coherence-violating logarithmic terms in LHC observables.

Objects subjected to a constant force generally increase their velocity over time. This expectation fails whenever their energy is a smooth and periodic function of momentum, resulting in periodic Bloch oscillations instead. Periodic dispersions, typical of lattice systems, can also emerge in continuum media through strong interactions. Here, we study the phenomenon of such Bloch oscillations in the absence of a lattice in a paradigmatic model of integrable quantum gases: the two-component Yang-Gaudin model. We derive a generalized-hydrodynamic theory of Bloch oscillations for a finite density of impurities embedded in a homogeneous interacting background, which we show to persist superimposed to a drift due to the acceleration of the center of mass. Moreover, we show the single-impurity oscillation period is renormalized at finite impurity density when two-magnon bound states are populated. Our results are relevant for ultracold atom experiments, where impurities can be created at controllable densities.

X-ray free-electron lasers (XFELs) enable the exploration of matter with atomic-scale spatiotemporal resolution. Generating radiation wavelengths below one angstrom is critical for applications such as crystallography and Mössbauer studies. Until now, achieving the subangstrom regime has required electron beam energies $\ge 8\mathrm{GeV}$ and undulator $K$ parameters $\ge 1.5$. In this Letter, we demonstrate the generation of high-power subangstrom FEL radiation using a 6.2 GeV electron beam and a $K$ parameter around unity and below. We show that exceptional electron beam brilliance—characterized by high peak current and low slice emittance—compensates for the reduced undulator coupling, enabling robust lasing. The demonstration was carried out at SwissFEL, where the subangstrom regime has already been successfully employed in user experiments. Our Letter paves the way for more compact and cost-effective accelerator designs through the optimization of electron beam quality.

We investigate the effects of disorder on a system that in the clean limit is a pair density wave (PDW) superconductor. The charge order of the clean PDW is inevitably lost (via Imry-Ma), but the fate of the superconducting order is less clear. Here, we consider a strongly inhomogeneous limit in which the system consists of a random collection of PDW puddles embedded in a metallic background. When the puddles are dilute, they become phase coherent at low temperatures, resulting in a state that is macroscopically equivalent to a charge-$2e$ $s$-wave superconductor. This is a mechanism by which a PDW can have zero resistance, even in the presence of disorder, and is thermodynamically distinct from the “vestigial” charge-$4e$ superconductivity that has been proposed to arise in weakly disordered PDWs.

We investigate lattice dynamics in ${\text{LaCoO}}_3$ using inelastic neutron and x-ray scattering over $\mathrm{T}=2-650\mathrm{K}$, spanning the spin-state crossover at ${\mathrm{T}}_1\approx 100\mathrm{K}$ and the insulator-metal transition at ${\mathrm{T}}_2\approx 550\mathrm{K}$. Comparison with quasiharmonic ab initio lattice-dynamical calculations helps reveal anomalous softening of $\mathrm{a}\approx 10\text{−}\mathrm{meV}$ oxygen phonon, confined to the temperature interval ${\mathrm{T}}_1\le \mathrm{T}\le {\mathrm{T}}_2$ and localized in momentum space at ${\mathbf{q}}_{\mathrm{SSO}}=(½,½,½{)}_{\mathrm{c}}$. This wave vector is characteristic of the spin-state-ordering pattern originally proposed by Goodenough [An interpretation of the magnetic properties of the perovskite-type mixed crystals ${\text{La}}_{1-\mathrm{x}}{\mathrm{Sr}}_{\mathrm{x}}{\text{CoO}}_{3-\lambda }$, J. Phys. Chem. Solids 6, 287 (1958)]. Our results provide momentum-resolved evidence for dynamic correlations of high-spin and low-spin ${\text{Co}}^{3+}$ states characterized by ${\mathbf{q}}_{\mathrm{SSO}}=(½,½,½{)}_{\mathrm{c}}$, demonstrating that phonons are sensitive probes of fluctuating spin-state correlations in ${\mathrm{LaCoO}}_3$.

Geometric frustration drives exotic quantum phases and transitions in condensed matter. One-dimensional frustrated magnets with inherent controllability are particularly promising for studying fundamental quantum physics, yet experimentally tunable systems remain scarce. Here, using first-principles calculations and confined structure search, we predict a novel one-dimensional platform: confined FeS nanotubes with twisted-triangular geometry. These nanotubes exhibit a triple-well energy landscape, hosting two ferroelectric and one paraelectric phases, exhibiting collinear antiferromagnetic and 120° noncollinear (NCL) orders, respectively. Application of axial strains tunes magnetic interactions and frustration, driving transitions from antiferromagnetic to NCL, and then to a double-cell NCL phase. The phase diagram can be described by a model with two dimensionless parameters. Large-scale tensor network simulations reveal starkly distinct chirality responses and magnetization plateaus under different magnitudes of magnetic fields for each phase, directly linking these behaviors to tunable frustration. Therefore, the multiferroic FeS nanotube provides a versatile platform for exploring electrically tunable quantum states, phase transitions, and field-induced phenomena associated with evolving magnetic frustration. This Letter establishes a general strategy combining first-principles prediction, confined structure search, and tensor networks for discovering and understanding frustrated low-dimensional quantum phenomena.

Layered Ising metamagnets are antiferromagnetic (AF) materials consisting of monolayer Ising ferromagnets coupled to each other via interlayer AF interactions. They exhibit rich magnetic phase diagrams, featuring tricritical and critical end points, due to the competing magnetic interactions and the Ising anisotropy. While conventional thermodynamic probes can identify these critical points in bulk Ising metamagnets, achieving this in the two-dimensional (2D) limit, where enhanced fluctuation effects can substantially modify critical phenomena, remains to be realized. Here, we combine a nanomechanical signal proportional to the specific heat capacity ($C_{\mathrm{V}}$) and magnetic circular dichroism measurements to identify these critical points, extract a tricritical exponent, and map out the complete magnetic phase diagram of 2D Ising metamagnetic ${\text{CrI}}_3$. This is achieved in a nanomechanical device of six-layer ${\text{CrI}}_3$, in which a direct measurement of the temperature derivative of its mechanical resonance frequency gives a signal proportional to $C_{\mathrm{V}}$. The tricritical point is identified by the onset of an abrupt spin-flip transition on one side and, on the other side, by a vanishing specific heat $\lambda$ anomaly for a continuous AF phase transition. In contrast, only the spin-flip transition remains near the critical end point. Our results establish nanomechanical calorimetry as a general route to classify metamagnetic phase transitions and to study multicritical phenomena in 2D magnets.

Chiral molecules have attracted significant multidisciplinary interest and extensive research owing to their remarkable ability to achieve charge-to-spin conversion, known as the chiral-induced spin selectivity (CISS). A recent experiment has revealed that chiral molecules also exhibit an unexpected capability for spin-to-charge conversion, referred to as the inverse CISS (ICISS), opening unprecedented avenues for the study and application of chiral molecules. Here, we propose a theoretical model, suggesting that ICISS can be understood in terms of spin-dependent electron deflection induced by the interplay between spin and chiral structure. Our numerical results are consistent with experimental observations, demonstrating that ICISS persists under strong disorder. Our model also reproduces the inverse spin Hall effect (ISHE) in this experiment. Comparative analysis indicates that ICISS exhibits a spin-to-charge conversion behavior that differs from ISHE. Our Letter develops a microscopic theoretical model that accounts for the experimentally observed phenomena, and may provide a useful perspective for organic spintronics.

A precision measurement of the muon charge asymmetry from $W$-boson decays in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ is presented. The analysis utilizes data corresponding to an integrated luminosity of $5.1{\mathrm{fb}}^{-1}$, recorded by the LHCb detector during 2016, 2017, and 2018. The asymmetry is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. This result represents the most precise determination of the muon charge asymmetry in the forward region to date, exhibiting excellent agreement with next-to-next-to-leading-order predictions in perturbative quantum chromodynamics. The measured asymmetries are corrected for experimental efficiencies, resolution, and final-state photon radiation.

High-intensity muon beams could enable a muonium-based axion search through resonant quantum transitions between hyperfine states. Combining theoretical calculations with simulation results, we demonstrate that such a muonium-based experimental approach could complement and tighten constraints on the axion-muon coupling beyond existing limits from the muon $g-2$ measurement over the axion mass range of $18–130\mathrm{\mu }\mathrm{eV}$. These results establish a new spectroscopic channel in muonium that enables searches for axion and axionlike particle dark matter.

We present measurements of the $\mathrm{K}{\alpha }_1$ and $\mathrm{K}{\alpha }_2$ natural x-ray linewidths of uranium, neptunium, and plutonium ($\mathrm{Z}=92$, 93, 94) obtained using a superconducting transition-edge sensor microcalorimeter array. The relative uncertainties range from 0.5% to 1.5%, improving upon previous values by factors ranging from 3 to 8. These refined linewidths reduce systematic errors in gamma-ray spectroscopy assays of Pu-bearing materials, where $\mathrm{K}\alpha$ x-rays overlap with diagnostic gamma lines. We also present multiconfiguration Dirac-Fock calculations of the $\mathrm{K}\alpha$ linewidths for U, Np, and Pu, providing a benchmark for theory and experiment. These calculations reveal a discrepancy between ab initio theory and experiment possible to observe only with the improved experimental accuracy achieved in this work.

Bound states in the continuum (BICs) have long been recognized as topological singularities of light, yet their descriptions have relied solely on scalar topological charges that trace a polarization angle rotation, leaving their true vectorial topology unexplored. Here, we apply the concept of a vectorial topological charge (VTC) to BICs, resolving this fundamental limitation by capturing the full set of winding numbers of ($S_1$, $S_2$, $S_3$) axes on the Poincaré sphere. Using bilayer photonic crystal slabs as a model system, we reveal that nontrivial VTCs can be manifested through pseudopolarization singularity generated by BICs within the perturbation parameter space. Intriguingly, such a VTC further links BICs to counterrotating phase singularities in the upward and downward radiation channels—an effect invisible in scalar frameworks. Moreover, the multicomponent nature of VTCs drives a BIC to split into multiple pairs of half-integer pseudopolarization singularities under symmetry breaking, rather than merely forming a pair of circular pseudopolarization states, thereby defying the conventional rules of topological charge evolution. Our findings reveal a richer vectorial topology that enables control of BICs beyond scalar descriptions.

The generation of energetic and dense plasmas by femtosecond laser pulses within the bulk of solids can pave the way to study warm dense matter, shocks, extreme UV radiation, or the synthesis of new material phases. However, this has remained elusive because of the intrinsic dynamical effects of defocusing by the laser-generated plasma. Here, we demonstrate the generation of overcritical plasma densities inside transparent solids over long distances. We identify with experiments in bulk sapphire and first-principles simulations that femtosecond conical interference via a Bessel beam creates a dense plasma rod of typically less than 400 nm diameter. We show that collisionless resonance absorption plays a primary role in the energy deposition process, yielding a plasma with an energy density on the order of $\mathrm{MJ}/{\mathrm{cm}}^3$, whose length can reach several cm using only tabletop femtosecond lasers. This opens new avenues for developing high-energy-density physics within solids.

A generalized ignition-accessibility framework is developed that unifies Lawson power balance, Cordey accessibility, the marginal ignition ridge, ignition entry points, and Mills thermal-runaway dynamics into a single self-consistent description of reactor-relevant burning plasmas. The 0D analysis recasts fusion ignition as a constrained dynamical pathway rather than a static threshold condition and demonstrates that radiation damping displaces the marginal ignition ridge, Cordey saddle, and ignition entry points toward higher densities and temperatures, thereby increasing the pressure required for ignition. In realistic 3D reactor geometry, this displacement translates into elevated plasma $\beta$ requirements, establishing a direct connection between power balance, ignition accessibility, and macroscopic magnetohydrodynamic stability limits. A generalized thermal-runaway analysis reveals a previously unrecognized stabilizing feedback arising from transport, impurity and synchrotron damping, and the universally unfavorable power scaling of energy confinement, capable of reducing runaway growth and enabling steady-state burn. Enhanced confinement and spin-polarized fuels partially reopen the ignition window toward near-ideal DT performance.