We have determined the fourth-order $n_f$ contributions to the two splitting functions governing the evolution of all flavor differences of quark distributions of hadrons in perturbative quantum chromodynamics with $n_f$ light flavors. The analytic forms of these functions are presented in both Mellin $N$ space and momentum-fraction $x$ space for a general gauge group. In the small-$x$ limit double logarithms occur, but the small-$x$ rise of both splitting functions is confined to extremely small-$x$ values, $x\lesssim {10}^{-6}$. The large-$x$ limit includes the $n_f$-part of the four-loop quark virtual anomalous dimension. Using this result we obtain also the $n_f$ contributions to the corresponding gluonic quantity and the complete threshold-enhanced logarithms from soft-gluon emission for a large class of inclusive observables, including Higgs boson production in gluon-gluon fusion.

We experimentally and numerically study the collapse dynamics of a quantum vortex in a two-dimensional atomic superfluid following a fast interaction ramp from repulsion to attraction. We find the conditions and timescales for a superfluid vortex to radially converge into a quasistationary density profile, demonstrating the spontaneous formation of a vortex solitonlike structure in an atomic Bose gas. We record an emergent self-similar dynamics caused by an azimuthal modulational instability, which amplifies initial density perturbations and leads to the eventual splitting of a solitonic ring profile or direct fragmentation of a superfluid into disordered, but roughly circular arrays of Townes solitonlike wave packets. These dynamics are qualitatively reproduced by simulations based on the Gross-Pitaevskii equation. However, a discrepancy in the magnitude of amplified density fluctuations predicted by our mean-field analysis suggests the presence of effects beyond the mean-field approximation. Our study sets the stage for exploring out-of-equilibrium dynamics of vortex quantum matter quenched to attractive interactions and their universal characteristics.

The relation between band topology and Majorana zero energy modes (MZMs) in topological superconductors had been well studied in the past decades. However, the relation between the quantum metric and MZMs has yet to be understood. In this Letter, we first construct a three band Lieb-like lattice model with an isolated flat band and tunable quantum metric. By introducing nearest neighbor equal spin pairing, we obtain the Lieb-Kitaev model which supports MZMs. When the Fermi energy is set within the flat band energy, the MZMs, which are supposed to be well localized at the ends of the 1D superconductor due to the flatness of the band, appear. On the contrary, we show both numerically and analytically that the localization length of the MZMs is controlled by a length scale defined by the quantum metric of the flat band, which we call the quantum metric length (QML). The QML can be several orders of magnitude longer than the conventional BCS superconducting coherence length. When the QML is comparable to the length of the superconductor, the two MZMs from the two ends of the superconductor can hybridize and induce ultra long range crossed Andreev reflections. This Letter unveils how the quantum metric can greatly influence the properties of MZMs through the QML, and the results can be generalized to other topological bound states.

Disorder and non-Hermitian effects together can upend how waves localize. In a 1D disordered chain, the non-Hermitian skin effect (NHSE) can induce Anderson delocalization, defying the usual rule that disorder in low dimensions always localizes states. While weak disorder leaves the NHSE intact, strong disorder restores Anderson localization. Here, we study a surprising twist: coupling a strongly disordered Hatano-Nelson chain to a disordered Hermitian chain with their disorder antisymmetrically correlated. Strikingly, once the interchain coupling exceeds a threshold, the system undergoes Anderson delocalization irrespective of disorder strength, reinstating the NHSE with no Hermitian counterpart. This transition arises from the interplay of nonreciprocal hopping, interchain coupling, and engineered disorder correlations, and is captured by a real-space winding number. To confirm this, we build an electrical-circuit analog and directly observe the reemergent NHSE via voltage measurements. Our Letter uncovers unexplored and experimentally accessible physics at the crossroads of non-Hermiticity and disorder.

Chiral phonons, which are characterized by rotational atomic motion, offer a unique mechanism for transferring angular momentum from phonons to electron spins and other angular momentum carriers. In this Letter, we present a theoretical investigation into the emergence of chiral phonons in a chiral hybrid organic-inorganic perovskite (HOIP) and their critical roles in rigid-body rotation, magnetic moment generation, and spin transport under nonthermal equilibrium conditions. We demonstrate that phonon angular momentum can modify the spin chemical potential via a proposed microscopic Barnett effect, leading to a spatially varying spin chemical potential at the metal/HOIP interface, which subsequently induces spin currents in an adjacent Cu layer, with a magnitude consistent with experimental observations. Additionally, we propose a mechanism for the intrinsic excitation of spin currents driven by chiral phonons under a parabolic temperature profile. Beyond their influence on spin transport, we also outline experimental approaches to probe chiral phonons through their distinctive mechanical and magnetic responses.

We propose a spatially inhomogeneous matrix product Ansatz for an exact many-body density operator of a boundary-driven $XXZ$ quantum circuit. The Ansatz has formally infinite bond dimension and is fundamentally different from previous constructions. The circuit is driven by a pair of reset quantum channels applied on the boundary qubits, which polarize the qubits to arbitrary pure target states. Moreover, one of the reset channels can be replaced by an arbitrary local unitary gate, thus representing a hybrid case with coherent and incoherent driving. Analyzing the Ansatz, we obtain a family of relatively robust separable nonequilibrium steady states, which can be viewed as a circuit extension of spin-helix states and are particularly suited for experimental investigations.

Using $e^{+}{e}^{-}$ collision data collected with the BESIII detector operating at the Beijing electron positron collider, the cross section of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{h}_c$ is measured at 59 points with center-of-mass energy $\sqrt{s}$ ranging from 4.009 to 4.950 GeV with a total integrated luminosity of $22.2{\mathrm{fb}}^{-1}$. The cross section between 4.3 and 4.45 GeV exhibits a plateaulike shape and drops sharply around 4.5 GeV, which cannot be described by two resonances only. Three coherent Breit-Wigner functions are used to parametrize the $\sqrt{s}$-dependent cross section line shape. The masses and widths are determined to be $M_1=({4223.6}_{-3.7-2.9}^{+3.6+2.6})\mathrm{MeV}/c^2$, ${\mathrm{\Gamma }}_1=({58.5}_{-11.4-6.5}^{+10.8+6.7})\mathrm{MeV}$, $M_2=({4327.4}_{-18.8-9.3}^{+20.1+10.7})\mathrm{MeV}/c^2$, ${\mathrm{\Gamma }}_2=({244.1}_{-27.1-18.3}^{+34.0+24.2})\mathrm{MeV}$, and $M_3=({4467.4}_{-5.4-2.7}^{+7.2+3.2})\mathrm{MeV}/c^2$, and ${\mathrm{\Gamma }}_3=({62.8}_{-14.4-7.0}^{+19.2+9.9})\mathrm{MeV}$. The first uncertainties are statistical and the second are systematic. The inclusion of the relatively narrower third component proves crucial for reproducing the drop at around 4.5 GeV. The statistical significance of the three-resonance assumption over the two-resonance assumption is greater than $5\sigma$.

Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow $v_2$ in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of $v_2$ of ${\pi }^{\pm }$, $K^{\pm }$, $K_S^0$, $p$, and $\mathrm{\Lambda }$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=3.2$, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of $v_2$ for all hadrons studied provides evidence for the onset of dominant partonic interactions by $\sqrt{s_{\mathrm{NN}}}=4.5\mathrm{GeV}$.

We report lifetime measurements of the metastable $6\mathrm{d}{}^2{\mathrm{D}}_{5/2}$ and $6\mathrm{d}{}^2{\mathrm{D}}_{3/2}$ states of ${\mathrm{Ra}}^{+}$. The measured lifetimes, ${\tau }_5=303.8(1.5)\mathrm{ms}$ and ${\tau }_3=642(9)\mathrm{ms}$, are important for optical frequency standards and for benchmarking high-precision relativistic atomic theory. Independent of the reported measurements, the D state lifetimes were calculated using the coupled-cluster single double triple method, in which the coupled-cluster equations for both core and valence triple excitations were solved iteratively. The method was designed for precise prediction of atomic properties, especially for heavy elements, where relativistic and correlation corrections become large, making their treatment more challenging. This Letter presents the first tests of the method for transition properties. Our prediction agrees with experimental values within the uncertainties. The ability to accurately predict the atomic properties of heavy elements is important for many applications, from tests of fundamental symmetries to the development of optical clocks.

While Andreev bound states (ABSs) have been realized in engineered superconducting junctions, their direct observation in normal metal-superconductor heterostructures—enabled by quantum confinement—remains experimentally elusive. Here, we report the detection of ABSs in ultrathin metallic islands (Bi, Ag, and SnTe) grown on the $s$-wave superconductor NbN. Using high-resolution scanning tunneling microscopy and spectroscopy, we clearly reveal in-gap ABSs with energies symmetric about the Fermi level. While the energies of these states show no position dependence, their wave functions exhibit spatial oscillations, demonstrating a quantum size effect. Both the energy levels and spatial distribution of the ABSs can be reproduced by our effective model in which a metallic island is coupled to the superconducting substrate via the proximity effect. We demonstrate that the coupling strength plays a critical role in determining the ABS energies. Our work introduces a novel physical platform for implementing ABSs, which hold promise for significant device applications.

The anomalous metal state (AMS), observed in “failed” superconductors, provides insights into superconductivity and quantum criticality, with studies revealing unconventional quantum phases like the Bose metal. Recently, layered transition metal dichalcogenide (TMD) superconductors approaching the two-dimensional limit have garnered significant attention for the enhanced phase fluctuations and electronic correlations. Investigating AMSs in these systems, particularly in the absence of an external magnetic field, could offer valuable insights into the dimensionality-driven emergence of exotic quantum phenomena, including triplet Cooper pairing, phase fluctuation dynamics, and especially the recently discovered field-free superconducting diode effects. However, the field-free AMS has yet to be observed in TMD superconductors. Here, we report the dimensionality-tunable AMS near the superconducting quantum phase transitions in a layered TMD superconductor $2\mathrm{H}\text{−}{\mathrm{Ta}}_2{\mathrm{S}}_3\text{Se}$. In samples with thicknesses below 10 nm, we demonstrate magnetic field-driven AMS under external magnetic field, characterized by the vanishing of the Hall resistance and the presence of finite longitudinal resistance. Remarkably, an unexpected zero-field AMS emerges as the sample thickness is reduced to 3 nm. This AMS aligns well with the quantum vortex creep model and exhibits nonreciprocal transport behaviors, suggesting the onset of spontaneous time-reversal symmetry breaking accompanied by vortex motion as the system approaches the two-dimensional limit. Our findings open new avenues for exploring dimensionality-driven exotic superconducting quantum critical phases and pave the way for a deeper understanding of zero-field superconducting diode effects.

We propose a model that is able to reproduce the type-II ultrafast demagnetization dynamics observed in 2D magnets. The spin system is coupled to the electronic thermal bath and is treated with atomistic spin dynamics, while the electron and phonon heat baths are described phenomenologically by coupled equations via the two-temperature model. Our proposed two-temperature model takes into account the effect of the heated substrate, which for 2D systems results in a slow demagnetization regime. We applied the framework to a generic 2D system, ${\mathrm{CrI}}_3$, and we are able to observe a type-II demagnetization process characterized by two steps, the first step being attributed to the free electrons generated when the system behaves as a quasimetal under optical excitation, and the second step, the slower demagnetization region, due to the heated substrate. Finally, after laser excitation, we are able to observe domain formation in ${\mathrm{CrI}}_3$, similar to recent experimental observations. Our generalized two-temperature model enhances the modeling of ultrafast magnetization dynamics processes by effectively describing the quasimetallic behavior of certain magnetic materials and the influence of a heated adjacent layer.

Soliton cores at the center of fuzzy dark matter (FDM) halos provide a promising way to distinguish FDM from other dark matter models. However, the relation between solitons and their host halos remains contentious. Here, we rigorously examine this soliton-halo relation (SHR) using a rich set of cosmological simulations across various FDM particle masses, halo masses, and redshifts. We explicitly demonstrate thermal equilibrium between solitons and surrounding halo granules, energy equipartition within halos, and an FDM concentration-mass-nonisothermality relation. For each FDM halo, we confirm that its density profile outside the central soliton matches a collisionless N-body simulation from the same initial condition, serving as stringent numerical convergence tests. Our refined SHR agrees well with virialized halos in simulations, with a $1\sigma$ deviation of less than 30%. These findings not only reaffirm the SHR proposed by Schive et al. [Understanding the core-halo relation of quantum wave dark matter from 3D simulations, Phys. Rev. Lett. 113, 261302 (2014)] but also offer a more comprehensive understanding that extends its applicability.

Space-based gravitational wave (GW) detectors, such as LISA, are expected to detect thousands of Galactic close white dwarf binaries emitting nearly monochromatic GWs. In this study, we demonstrate that LISA is reasonably likely to detect higher harmonic GW signals, particularly the $(l,|m|)=(3,3)$ mode, from a limited sample of nearby close white dwarf binaries, even with small orbital velocities $v/c$ of order ${10}^{-3}$. The amplitudes of these post-Newtonian modes provide robust probes of mass asymmetry in such systems, making them valuable observational targets, especially in mass-transferring binaries. Long-term, coordinated detector operations will further improve the prospects for detecting these informative signals.

The Hamiltonian formulation of the BMS symmetry on spacelike hypersurfaces enables one to define its action on solutions of the Wheeler-DeWitt equation. Using the Becchi-Rouet-Stora-Tyutin (BRST) reformulation of the theory, we provide operator expressions for the matrix elements of the BMS operators between Wheeler-DeWitt states. To that end, we construct the BRST-invariant extensions of the BMS generators, which form a BRST extension of the BMS algebra.

The first search for a heavy neutral spin-1 gauge boson ($Z^{\prime }$) with nonuniversal fermion couplings produced via vector boson fusion processes and decaying to tau leptons or $W$ bosons is presented. The analysis is performed using LHC data at $\sqrt{s}=13\mathrm{TeV}$, collected from 2016 to 2018 with the CMS experiment and corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. The data are consistent with the standard model predictions. Upper limits are set on the product of the cross section for production of the $Z^{\prime }$ boson and its branching fraction to $\tau \tau$ or $WW$. The presence of a $Z^{\prime }$ boson decaying to ${\tau }^{+}{\tau }^{-}$ ($W^{+}{W}^{-}$) is excluded for masses up to 2.45(1.60) TeV, depending on the $Z^{\prime }$ boson coupling to standard model weak bosons, and assuming a $Z^{\prime }\to {\tau }^{+}{\tau }^{-}$ ($W^{+}{W}^{-}$) branching fraction of 50%.

We report on numerical predictions and experimental observations of a novel type of temporal localized dissipative structures that manifest themselves in the self-defocusing regime of driven nonlinear optical resonators with two polarization modes. These chiral dissipative solitons, which we term “polarization faticons,” break both temporal and polarization symmetry and consist of two bright lobes of opposite polarization handedness, interlocked by a domain wall. Our study reveals that faticons are connected to a vectorial modulational instability, from which they can be excited through a collapsing dynamic. Faticons could offer a novel pathway for frequency comb generation in normal dispersion resonators. More generally, they offer new fundamental insights into vectorial localized dissipative structures and could be relevant to other multicomponent dissipative systems.