We report constraints on the dark photon effective kinetic mixing parameter ($\kappa$) with data taken from two $p$-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on $\kappa$ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses ($m_V$) from 10 to $300\mathrm{eV}/c^2$ in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with $m_V$ from 0.1 to $4.0\mathrm{keV}/c^2$ are set from 449.6 kg-day data, with a minimum of $\kappa =1.3\times {10}^{-15}$ at ${\mathrm{m}}_{\mathrm{V}}=200\mathrm{eV}/{\mathrm{c}}^2$.

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions and allow searches for physics beyond the standard model. We present the first results on isospin amplitudes in $b$-baryon decays, using data corresponding to an integrated luminosity of $8.5{\mathrm{fb}}^{-1}$, collected with the LHCb detector in $pp$ collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio $|A_1({\mathrm{\Lambda }}_b^0\to J/\psi {\mathrm{\Sigma }}^0)/A_0({\mathrm{\Lambda }}_b^0\to J/\psi \mathrm{\Lambda })|$, where the subscript on $A$ indicates the final-state isospin, is measured to be less than $1/21.8$ at 95% confidence level. The Cabibbo suppressed ${\mathrm{\Xi }}_b^0\to J/\psi \mathrm{\Lambda }$ decay is observed for the first time, allowing for the measurement $|A_0({\mathrm{\Xi }}_b^0\to J/\psi \mathrm{\Lambda })/A_{1/2}({\mathrm{\Xi }}_b^0\to J/\psi {\mathrm{\Xi }}^0)|=0.37\pm 0.06\pm 0.02$, where the uncertainties are statistical and systematic, respectively.

We study inclusive and diffractive dijet production in electron-proton and electron-nucleus collisions within the color glass condensate effective field theory. We compute dijet cross sections differentially in both mean dijet transverse momentum $\mathit{P}$ and recoil momentum $\mathbf{\Delta }$, as well as the anisotropy in the relative angle between $\mathit{P}$ and $\mathbf{\Delta }$. Our results cover a much larger kinematic range than accessible in previous computations performed in the correlation limit approximation, where it is assumed that $|\mathit{P}|\gg |\mathbf{\Delta }|$. We validate this approximation in its range of applicability and quantify its failure for $|\mathit{P}|\lesssim |\mathbf{\Delta }|$. We also predict significant target-dependent deviations from the correlation limit approximation for $|\mathit{P}|>|\mathbf{\Delta }|$ and $|\mathit{P}|\lesssim Q_s$, which offers a straightforward test of gluon saturation and access to multigluon distributions at a future Electron-Ion Collider.

Intermolecular processes offer unique decay mechanisms for complex systems to internally relax. Here, we report the observation of an intermolecular Coulombic decay channel in an endohedral fullerene, a holmium nitride complex (${\mathrm{Ho}}_3\mathrm{N}$) embedded within a ${\mathrm{C}}_{80}$ fullerene, between neighboring holmium ions, and between the holmium complex and the carbon cage. By measuring the ions and the electrons in coincidence after XUV photoabsorption, we can isolate the different decay channels, which are found to be more prevalent relative to intra-atomic Auger decay.

Photoelectron spectra obtained with intense pulses generated by free-electron lasers through self-amplified spontaneous emission are intrinsically noisy and vary from shot to shot. We extract the purified spectrum, corresponding to a Fourier-limited pulse, with the help of a deep neural network. It is trained on a huge number of spectra, which was made possible by an extremely efficient propagation of the Schrödinger equation with synthetic Hamilton matrices and random realizations of fluctuating pulses. We show that the trained network is sufficiently generic such that it can purify atomic or molecular spectra, dominated by resonant two- or three-photon ionization, nonlinear processes which are particularly sensitive to pulse fluctuations. This is possible without training on those systems.

The prominent Dicke superradiant phase arises from coupling an ensemble of atoms to a cavity optical field when an external optical pumping exceeds a threshold strength. Here we report a prediction of the superradiant instability driven by Anderson localization, realized with a hybrid system of the Dicke and Aubry-André (DAA) model for bosons trapped in a one-dimensional (1D) quasiperiodic optical lattice and coupled to a cavity. Our central finding is that for bosons condensed in a localized phase given by the DAA model, the resonant superradiant scattering is induced, for which the critical optical pumping of the superradiant phase transition approaches zero, giving an instability driven by the Anderson localization. The superradiant phase for the DAA model with or without a mobility edge is investigated, showing that the localization driven superradiant instability is in sharp contrast to the superradiance as widely observed for a Bose-Einstein condensate in extended states, and should be insensitive to the temperature of the system. This study unveils a novel effect of localization on the Dicke superradiance, and is well accessible based on the current experiments.

We study the competition between local (bridging) and global condensation of fluid in a chemically heterogeneous capillary slit made from two parallel adjacent walls each patterned with a single stripe. Using a mesoscopic modified Kelvin equation, which determines the shape of the menisci pinned at the stripe edges in the bridge phase, we determine the conditions under which the local bridging transition precedes capillary condensation as the pressure (or chemical potential) is increased. Provided the contact angle of the stripe is less than that of the outer wall we show that triple points, where evaporated, locally condensed, and globally condensed states all coexist are possible depending on the value of the aspect ratio $a=L/H$, where $H$ is the stripe width and $L$ the wall separation. In particular, for a capillary made from completely dry walls patterned with completely wet stripes the condition for the triple point occurs when the aspect ratio takes its maximum possible value $8/\pi$. These predictions are tested using a fully microscopic classical density functional theory and shown to be remarkably accurate even for molecularly narrow slits. The qualitative differences with local and global condensation in heterogeneous cylindrical pores are also highlighted.

Correlated charge inhomogeneity breaks the electron-hole symmetry in two-dimensional (2D) bilayer heterostructures which is responsible for nonzero drag appearing at the charge neutrality point. Here we report Coulomb drag in novel drag systems consisting of a two-dimensional graphene and a one-dimensional (1D) InAs nanowire (NW) heterostructure exhibiting distinct results from 2D-2D heterostructures. For monolayer graphene (MLG)-NW heterostructures, we observe an unconventional drag resistance peak near the Dirac point due to the correlated interlayer charge puddles. The drag signal decreases monotonically with temperature ($\sim T^{-2}$) and with the carrier density of NW ($\sim n_N^{-4}$), but increases rapidly with magnetic field ($\sim B^2$). These anomalous responses, together with the mismatched thermal conductivities of graphene and NWs, establish the energy drag as the responsible mechanism of Coulomb drag in MLG-NW devices. In contrast, for bilayer graphene (BLG)-NW devices the drag resistance reverses sign across the Dirac point and the magnitude of the drag signal decreases with the carrier density of the NW ($\sim n_N^{-1.5}$), consistent with the momentum drag but remains almost constant with magnetic field and temperature. This deviation from the expected $T^2$ arises due to the shift of the drag maximum on graphene carrier density. We also show that the Onsager reciprocity relation is observed for the BLG-NW devices but not for the MLG-NW devices. These Coulomb drag measurements in dimensionally mismatched (2D-1D) systems, hitherto not reported, will pave the future realization of correlated condensate states in novel systems.

Understanding the origin of the magnetism of high temperature superconductors is crucial for establishing their unconventional pairing mechanism. Recently, theory predicts that FeSe is close to a magnetic quantum critical point, and thus weak perturbations such as impurities could induce local magnetic moments. To elucidate such quantum instability, we have employed scanning tunneling microscopy and spectroscopy. In particular, we have grown FeSe film on superconducting Pb(111) using molecular beam epitaxy and investigated magnetic excitation caused by impurities in the proximity-induced superconducting gap of FeSe. Our study provides deep insight into the origin of the magnetic ordering of FeSe by showing the way local magnetic moments develop in response to impurities near the magnetic quantum critical point.

We experimentally identify coherent spin pumping in the magnon-magnon hybrid modes of yttrium iron garnet/permalloy (YIG/Py) bilayers. By reducing the YIG and Py thicknesses, the strong interfacial exchange coupling leads to large avoided crossings between the uniform mode of Py and the spin wave modes of YIG enabling accurate determination of modification of the linewidths due to the dampinglike torque. We identify additional linewidth suppression and enhancement for the in-phase and out-of-phase hybrid modes, respectively, which can be interpreted as concerted dampinglike torque from spin pumping. Furthermore, varying the Py thickness shows that both the fieldlike and dampinglike couplings vary like $1/\sqrt{t_{\mathrm{Py}}}$, verifying the prediction by the coupled Landau-Lifshitz equations.

The 2D Hubbard model with nearest-neighbor hopping on the square lattice and an average of one electron per site is known to undergo an extended crossover from metallic to insulating behavior driven by proliferating antiferromagnetic correlations. We study signatures of this crossover in spin and charge correlation functions and present results obtained with controlled accuracy using the diagrammatic Monte Carlo approach in the range of parameters amenable to experimental verification with ultracold atoms in optical lattices. The qualitative changes in charge and spin correlations associated with the crossover are observed at well-separated temperature scales, which encase the intermediary regime of non-Fermi-liquid character, where local magnetic moments are formed and nonlocal fluctuations in both channels are essential.

Complex liquids flow is known to be drastically affected by the roughness condition at the interfaces. We combined stresses measurements and observations of the flow during the motion of different rough surfaces in dry liquid foams. We visually show that three distinct friction regimes exist: slippage, stick-slip motion, and anchored soap films. Our stress measurements are validated for slippage and anchored regimes based on existing models, and we propose a leverage rule to describe the stresses during the stick-slip regime. We find that the occurrence of the stick-slip or anchored regimes is controlled by the roughness factor, defined as the ratio between the size of the surface asperities and the radius of curvature of the Plateau borders.

We experimentally studied the shear effect on dynamical heterogeneity near glass transition temperature. X-ray photon correlation spectroscopy was utilized to study the dynamics of polyvinyl acetate with tracer particles near its glass transition temperature, to determine the local shear rate from the anisotropic behavior of the time autocorrelation function and to calculate the dynamical heterogeneity using higher-order correlation function. The obtained results show a decrease in the dynamical heterogeneity and faster dynamics with increasing shear rate. This is the first experimental result that proved the predictions of previous molecular dynamics simulations.

We present a theory of chemokinetic search agents that regulate directional fluctuations according to distance from a target. A dynamic scattering effect reduces the probability to penetrate regions with high fluctuations and thus reduces search success for agents that respond instantaneously to positional cues. In contrast, agents with internal states that initially suppress chemokinesis can exploit scattering to increase their probability to find the target. Using matched asymptotics between the case of diffusive and ballistic search, we obtain analytic results beyond Fox colored noise approximation.

A generalization of quantum discord to multipartite systems is proposed. A key feature of our formulation is its consistency with the conventional definition of discord in bipartite systems. It is by construction zero only for systems with classically correlated subsystems and is a non-negative quantity, giving a measure of the total nonclassical correlations in the multipartite system with respect to a fixed measurement ordering. For the tripartite case, we show that the discord can be decomposed into contributions resulting from changes induced by nonclassical correlation breaking measurements in the conditional mutual information and tripartite mutual information. The former gives a measure of the bipartite nonclassical correlations and is a non-negative quantity, while the latter is related to the monogamy of the nonclassical correlations.

We propose a time-of-arrival operator in quantum mechanics by conditioning on a quantum clock. This allows us to bypass some of the problems of previous proposals, and to obtain a Hermitian time of arrival operator whose probability distribution arises from the Born rule and which has a clear physical interpretation. The same procedure can be employed to measure the “time at which some event happens” for arbitrary events (and not just specifically for the arrival time of a particle).

A remarkable feature of quantum many-body systems is the orthogonality catastrophe that describes their extensively growing sensitivity to local perturbations and plays an important role in condensed matter physics. Here we show that the dynamics of the orthogonality catastrophe can be fully characterized by the quantum speed limit and, more specifically, that any quenched quantum many-body system, whose variance in ground state energy scales with the system size, exhibits the orthogonality catastrophe. Our rigorous findings are demonstrated by two paradigmatic classes of many-body systems—the trapped Fermi gas and the long-range interacting Lipkin-Meshkov-Glick spin model.

The Rényi entanglement entropy in quantum many-body systems can be viewed as the difference in free energy between partition functions with different trace topologies. We introduce an external field $\lambda$ that controls the partition function topology, allowing us to define a notion of nonequilibrium work as $\lambda$ is varied smoothly. Nonequilibrium fluctuation theorems of the work provide us with statistically exact estimates of the Rényi entanglement entropy. This framework also naturally leads to the idea of using quench functions with spatially smooth profiles, providing us a way to average over lattice scale features of the entanglement entropy while preserving long distance universal information. We use these ideas to extract universal information from quantum Monte Carlo simulations of SU($N$) spin models in one and two dimensions. The vast gain in efficiency of this method allows us to access unprecedented system sizes up to $192\times 96$ spins for the square lattice Heisenberg antiferromagnet.

One of the major open questions in particle physics is the issue of the neutrino mass ordering (NMO). The current data of the two long-baseline experiments $\mathrm{NO}\nu \mathrm{A}$ and T2K, interpreted in the standard three-flavor scenario, provide a $\sim 2.4\sigma$ indication in favor of the normal neutrino mass ordering. We show that such an indication is completely washed out if one assumes the existence of neutral-current nonstandard interactions (NSI) of the flavor changing type involving the $e-\tau$ flavors. This implies that the claim for a discovery of the NMO will require a careful consideration of the impact of hypothetical NSI.