In this Letter, we report the dark matter search results from the commissioning run (Run0) and the first science run (Run1) of the PandaX-4T experiment. The two datasets were processed with a unified procedure, with the Run1 data treated blindly. The data processing is improved compared to previous work, unifying the low-level signal reconstruction in a wide energy range up to 120 keV. With a total exposure of $1.54\mathrm{tonne}·\mathrm{year}$, no significant excess of nuclear recoil events is found. The lowest 90% confidence level exclusion on the spin-independent cross section is $1.6\times {10}^{-47}{\mathrm{cm}}^2$ at a dark matter mass of $40\mathrm{GeV}/c^2$. Our results represent the most stringent constraint for a dark matter mass above $100\mathrm{GeV}/c^2$.

Isoscalar dipole transitions are a distinctive fingerprint of cluster structures. A $1^{-}$ resonance at 7.27(10) MeV, located just below the $\alpha$-emission threshold, has been observed in the deuteron inelastic scattering reactions off ${}^{10}\mathrm{Be}$. The deformation lengths of the excited states in ${}^{10}\mathrm{Be}$ below 9 MeV have been inferred from the differential cross sections using coupled channel calculations. This observed $1^{-}$ resonance has isoscalar characteristics and exhausts approximately 5%–15% of the isoscalar dipole energy-weighted sum rule, providing evidence for pronounced $\alpha$ cluster structure in ${}^{10}\mathrm{Be}$. The Gamow coupled channel approach supports this interpretation and suggests the near-threshold effect might be playing an important role in this excitation energy domain. The $\alpha +\alpha +n+n$ four-body calculation reproduces the observed enhanced dipole strength, implying that the four-body cluster structure is essential to describe the $1^{-}$ states in ${}^{10}\mathrm{Be}$.

We study spontaneous photon decay into multiple photons triggered by strong nonlinearities in an experimental simulator of a bosonic quantum impurity model. Previously, spectroscopic signatures of photon conversion were reported and evidenced as resonances in the many-body spectrum of these systems. Here, we report on the observation of multimode fluorescence of a small Josephson junction embedded in a high impedance superconducting transmission line. Measurement of the down-converted photons is achieved using state-of-the-art broadband parametric amplifiers. Photon triplet emission is explicitly demonstrated at a given frequency as the counterpart of inelastic photon decay at $3\times$ the emission frequency. These results open exciting prospects for the burgeoning field of many-body quantum optics and offer a direct signature of the ultrastrong light-matter coupling.

Density-functional theory (DFT) within the Kohn-Sham (KS) formalism is the most widely used approach to treat electronic structures of molecules and solids in physics, chemistry, and materials science, and the development of more accurate functionals for the KS exchange and correlation energy has been a major research focus for decades. The corresponding exchange and correlation potentials, on the other hand, have attracted little attention. Those cases for which reference potentials are available showed that in particular correlation potentials from common approximate density functionals are of poor quality and sometimes have little in common with the exact potentials. This hampers the further development of KS-DFT. Here, we show that highly accurate correlation potentials can be obtained within the random phase approximation (RPA). In conjunction with the exact exchange potential, which, like the RPA correlation potential, is accessible within the optimized effective potential method, highly accurate exchange-correlation potentials are available and provide a basis for the further development of DFT. We present a numerically stable approach for efficiently carrying out self-consistent RPA calculations and combine it with a KS inversion method to obtain reference correlation potentials from highly accurate electron densities from coupled cluster calculations. Accurate exchange-correlation potentials have to yield KS eigenvalues for the highest occupied molecular orbital that are close to the negative of the ionization potential. This is indeed the case, the RPA highest occupied molecular orbital eigenvalues yield ionization potentials that can compete with $GW$ ionization potentials.

We study two related universal anomalies of the spectral function of cuprates, so-called waterfall and high-energy kink features, by a combined cellular dynamical mean-field theory and angle-resolved photoemission study for the oxychloride ${\mathrm{Na}}_x{\mathrm{Ca}}_{2-x}{\mathrm{CuO}}_2{\mathrm{Cl}}_2$ (Na-CCOC). Tracing their origin back to an interplay of spin-polaron and local-correlation effects both in undoped and hole-doped (Na-)CCOC, we establish them as a universal crossover between regions differing in the momentum dependence of the coupling and not necessarily in the related quasiparticles’ energies. The proposed scenario extends to doping levels coinciding with the cuprate’s superconducting dome and motivates further investigations of the fate of spin polarons in the superconducting phase.

Elections for public offices in democratic nations are large-scale examples of collective decision-making. As a complex system with a multitude of interactions among agents, we can anticipate that universal macroscopic patterns could emerge independent of microscopic details. Despite the availability of empirical election data, such universality, valid at all scales, countries, and elections, has not yet been observed. In this Letter, we propose a parameter-free voting model and analytically show that the distribution of the victory margin is driven by that of the voter turnout, and a scaled measure depending on margin and turnout leads to a robust universality. This is demonstrated using empirical election data from 34 countries, spanning multiple decades and electoral scales. The deviations from the model predictions and universality indicate possible electoral malpractices. We argue that this universality is a stylized fact indicating the competitive nature of electoral outcomes.

We show that noisy quantum dynamics exposed to generalized measurements exhibit a spectral transition between gapless and gapped phases. To this end, we employ the Lyapunov spectrum obtained through singular values of a nonunitary matrix describing the dynamics. We discover that the gapless and gapped phases, respectively, correspond to the volume-law and area-law phases of the entanglement entropy for the dominant Lyapunov vector. This correspondence between the spectral gap and the scaling of entanglement offers an intriguing common structure with ground-state phase transitions. We also discuss some crucial differences from ground-state transitions, such as the extensive entanglement and the exponentially small gaps. Furthermore, we show that the spectral transition leads to the transition of the timescale for the memory loss and purification of initial states.

We calculate the leading and next-to-leading corrections to the real-time QCD static potential in a high-temperature medium in the region where bound states transit from narrow resonances to wide ones. We find sizable contributions to both the real and the imaginary part of the potential. The calculation involves both loop diagrams calculated in the hard thermal loop effective theory and power corrections to the hard thermal loop Lagrangian calculated in QCD. We compare our results with recent lattice data and check the consistency of different methods used in lattice calculations. We also discuss the usefulness of our results to guide lattice inputs.

We study and characterize a quasicontinuous dynamical decoupling scheme that effectively suppresses dominant frequency shifts in a multi-ion optical clock. Addressing the challenge of inhomogeneous frequency shifts in such systems, our scheme mitigates primary contributors, namely, the electric quadrupole and the linear Zeeman shifts. Based on ${}^{88}{\mathrm{Sr}}^{+}$ ions, we implement the scheme in linear chains of up to 7 ions and demonstrate a significant suppression of the shift by more than 3 orders of magnitude, leading to relative frequency inhomogeneity below $7\times {10}^{-17}$. Additionally, we evaluate the associated systematic shift arising from the radio-frequency drive used in the QCDD scheme, showing that, in the presented realization, its contribution to the systematic relative frequency uncertainty is below ${10}^{-17}$, with the potential for further improvement. These results provide a promising avenue toward implementing multi-ion clocks exhibiting an order of magnitude or more improvement in stability while maintaining a similar high degree of accuracy to that of single-ion clocks.

In this work, we develop a perturbation theory to analyze resonant states near a bound state in the continuum (BIC) in photonic crystal slabs. The theory allows us to rigorously determine the asymptotic behavior of $Q$-factor and the far-field polarization. We show that the resonant states close to a BIC can be nearly circularly polarized if the scattering matrix satisfies a certain condition. Moreover, our theory offers a novel perspective on super-BICs and provides a clear and precise condition to efficiently identify them in both symmetric and asymmetric structures without requiring a merging process. For practical applications, we find a super-BIC in a square lattice of rods on a dielectric substrate. Our theory addresses the non-Hermitian nature of the system, can be generalized to treat other structures that support BICs, and has potential applications in resonance and chiral optics.

Traditional ferroelectrics are limited by Neumann’s principle, which confines exploration of ferroelectrics within polar point groups. Our recent work [Ji et al., Nat. Commun. 15, 135 (2024)] proposes the concept of fractional quantum ferroelectricity (FQFE) that extends the playground of ferroelectricity to nonpolar point groups. Here, we apply group theory and introduce an efficient symmetry strategy to identify FQFE candidates. Integrated with a high-throughput screening scheme, we go through 171 527 materials and identify 221 potential FQFE candidates, which are already experimentally synthesized. In addition, we point out for the first time that the essence of FQFE is fractional atomic displacements with respect to lattice vectors, which can actually result in both fractional (type I) and integer (type II) quantized polarization, respectively. Through performing first-principles calculations, we verify the symmetry-predicted switchable FQFE properties in bulk ${\mathrm{AlAgS}}_2$ and monolayer ${\mathrm{HgI}}_2$. Notably, ${\mathrm{AlAgS}}_2$ exhibits an ultralow switching barrier of $22\mathrm{meV}/\mathrm{f}.\mathrm{u}.$ and interlocked in-plane/out-of-plane polarization, while ${\mathrm{HgI}}_2$ displays large spontaneous polarization of $42\mathrm{\mu }\mathrm{C}/{\mathrm{cm}}^2$. Our findings not only advance the understanding on FQFE, but also offer guidance for experimental exploration and design of novel ferroelectric materials.

Employing a two-species Cahn-Hilliard model with nonreciprocal interactions, we show that the interplay of nonreciprocity and conservation laws results in the robust coexistence of uniform stationary and oscillatory phases as well as of uniform and crystalline phases. For nonequilibrium models with a spurious gradient dynamics structure, such coexistences between two or more nonequilibrium phases and resulting phase diagrams can, nevertheless, be predicted by a Maxwell double-tangent construction. This includes phases with sustained regular or irregular out-of-equilibrium dynamics as further corroborated by bifurcation studies and time simulations.

“A battery powers a device” can be read as “work stored in the battery is being transported to the device.” In quantum batteries, the total amount of stored work can be measured by ergotropy, which is the maximal work extractable by unitary operations. Transporting ergotropy is fundamentally different from transporting energy, and here we find that ergotropy can be gained even when the transmission channel is strictly energy conserving. We show that, generically, ergotropy transport is lossy whenever the two systems start uncorrelated. In contrast, for a large class of correlated initial states, transport can be gainful. Furthermore, a single correlated state can be used multiple times, allowing to transport without losses an order of magnitude more work than the battery capacity. Correlations are thus a useful resource for ergotropy transport, and we quantify how this resource is consumed during gainful transport.

The Kibble-Zurek mechanism predicts a universal scaling behavior of the defect production when a system is slowly quenched across a critical phase transition point. Here, we discover that the universal scaling behavior across a higher-order topological phase transition does not conform to the traditional Kibble-Zurek mechanism. To explain the anomalous scaling exponent, we develop a solvable Landau-Zener model that takes into account the role of topological edge band that dominates the phase transition. For a two-dimensional boundary-obstructed higher-order topological system, the Kibble-Zurek scaling must be modified to adopt the effective dimension of topological edge band instead of the real physical dimension. We also find that across the boundary-obstructed higher-order topological phase transition, boundary conditions can drastically modify the scaling behaviors. For comparison, we investigate the slow quench dynamics across the bulk-obstructed phase transitions and a single multicritical point, which obeys the Kibble-Zurek mechanism with physical dimension.

We consider the estimation of an unknown parameter $\theta$ through a quantum probe at thermal equilibrium. The probe is assumed to be in a Gibbs state according to its Hamiltonian $H_{\theta }$, which is divided in a parameter-encoding term $H_{\theta }^{\mathrm{P}}$ and an additional, parameter-independent control $H^{\mathrm{C}}$. Given a fixed encoding, we find the maximal quantum Fisher information attainable via arbitrary $H^{\mathrm{C}}$, which provides a fundamental bound on the measurement precision. We elucidate the role of quantum coherence between encoding and control in different temperature regimes, which include ground state metrology as a limiting case. In the case of locally encoded parameters, the optimal sensitivity presents an $N^2$ scaling in terms of the number of particles of the probe, which can be reached, at finite temperature, with local measurements and no entanglement. We apply our results to paradigmatic spin chain models, showing that these fundamental limits can be approached using local two-body interactions. Our results set the fundamental limits and optimal control for metrology with thermal and ground state probes, including probes at the verge of criticality.

Stellar evolution theories predict a gap in the black hole birth mass spectrum as the result of pair instability processes in the cores of massive stars. This gap, however, is not seen in the binary black hole masses inferred from gravitational wave data. One explanation is that black holes form dynamically in dense star clusters where smaller black holes merge to form more massive black holes, populating the mass gap. We show that this model predicts a distribution of the effective and precessing spin parameters, ${\chi }_{\mathrm{eff}}$ and ${\chi }_{\mathrm{p}}$, within the mass gap that is insensitive to assumptions about black hole natal spins and other astrophysical parameters. We analyze the distribution of ${\chi }_{\mathrm{eff}}$ as a function of primary mass for the black hole binaries in the third gravitational wave transient catalog. We infer the presence of a high mass and isotropically spinning population of black holes that is consistent with hierarchical formation in dense star clusters and a pair-instability mass gap with a lower edge at ${44}_{-4}^{+6}{M}_{\odot }$. We compute a Bayes factor $\mathcal{B}>{10}^4$ relative to models that do not allow for a high mass population with a distinct ${\chi }_{\mathrm{eff}}$ distribution. Upcoming data will enable us to tightly constrain the hierarchical formation hypothesis and refine our understanding of binary black hole formation.

We perform the first amplitude analysis of $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0$ decays based on data samples of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of $7.33{\mathrm{fb}}^{-1}$. We report the observation of $D_s^{+}\to f_0(980)\rho (770{)}^{+}$ with a statistical significance greater than $10\sigma$ and determine the branching fractions $\mathcal{B}(D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0{|}_{\mathrm{non}-\eta })=(2.04\pm 0.08_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}})\%$ and $\mathcal{B}(D_s^{+}\to \eta {\pi }^{+})=(1.56\pm 0.09_{\mathrm{stat}}\pm 0.04_{\mathrm{syst}})\%$. Moreover, we measure the relative branching fraction between $\varphi \to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\varphi \to K^{+}{K}^{-}$ to be $[\mathcal{B}(\varphi (1020)\to {\pi }^{+}{\pi }^{-}{\pi }^0)/\mathcal{B}(\varphi (1020)\to K^{+}{K}^{-})]=0.230\pm 0.014_{\mathrm{stat}}\pm 0.010_{\mathrm{syst}}$., which deviates from the world average value by more than $4\sigma$.

Topological defects are nonsmooth field configurations with singularities that widely exist in physics and multidisciplinary areas. Here, we introduce near-field polarization evolution and the resulting topological spin states in a system of silicon-based coupled waveguides. The topological spin structures originate from 3D evanescent field coupling that transforms the trivial transverse spin into the topological spin states in a 2D plane. Moreover, we show that the periodic coupling of higher-order electromagnetic modes can produce intriguing spin defect (singularity) arrays, including those with alternately topological charges of $\pm 1$. These findings may further expand the family of electromagnetic topological structures, and open new avenues to engineer photon emission and light-matter interactions on integrated photonic platforms.