The rotational and translational dynamics of molecular hydrogen trapped within $\beta$-hydroquinone clathrate (${\mathrm{H}}_2@\beta$-HQ)—a practical example of a quantum particle trapped within an anisotropic confining potential—were investigated using inelastic neutron scattering and Raman spectroscopy. High-resolution vibrational spectra, including those collected from the VISION spectrometer at Oak Ridge National Laboratory, indicate relatively strong attractive interaction between guest and host with a strikingly large splitting of rotational energy levels compared with similar guest-host systems. Unlike related molecular systems in which confined ${\mathrm{H}}_2$ exhibits nearly free rotation, the behavior of ${\mathrm{H}}_2@\beta$-HQ is explained using a two-dimensional (2D) hindered rotor model with barrier height more than 2 times the rotational constant ($-16.2\mathrm{meV}$).

We consider a regular assembly of singly occupied cells with two accessible volumes. Coupled to cell volumes are interaction energies between nearest neighbors that lead to a phase transition with a critical point. We find that these compressible cell models can serve as Ising-like prototypes of the one-component liquid-liquid and isostructural solid-solid phase transitions that originate in the short-range features of the intermolecular potential. The mean-field solutions provide hints concerning the analytical form of the equation of state of liquid water.

Milagro observations have found bright, diffuse TeV emission concentrated along the galactic plane of the Milky Way. The intensity and spectrum of this emission is difficult to explain with current models of hadronic $\gamma$-ray production, and has been named the “TeV excess.” We show that TeV emission from pulsars naturally explains this excess. Recent observations have detected “TeV halos” surrounding pulsars that are either nearby or particularly luminous. Extrapolating this emission to the full population of Milky Way pulsars indicates that the ensemble of “subthreshold” sources necessarily produces bright TeV emission diffusively along the Milky Way plane. Models indicate that the TeV halo $\gamma$-ray flux exceeds that from hadronic $\gamma$ rays above an energy of $\sim 500\mathrm{GeV}$. Moreover, the spectrum and intensity of TeV halo emission naturally matches the TeV excess. Finally, we show that upcoming HAWC observations will resolve a significant fraction of the TeV excess into individual TeV halos, conclusively confirming, or ruling out, this model.

We derive an analytic representation of the ten-particle, two-loop double-box integral as an elliptic integral over weight-three polylogarithms. To obtain this form, we first derive a fourfold, rational (Feynman-)parametric representation for the integral, expressed directly in terms of dual-conformally invariant cross ratios; from this, the desired form is easily obtained. The essential features of this integral are illustrated by means of a simplified toy model, and we attach the relevant expressions for both integrals in ancillary files. We propose a normalization for such integrals that renders all of their polylogarithmic degenerations pure, and we discuss the need for a new “symbology” of mixed iterated elliptic and polylogarithmic integrals in order to bring them to a more canonical form.

A measurement is reported of the ratio of branching fractions $\mathcal{R}(J/\psi )=\mathcal{B}(B_c^{+}\to J/\psi {\tau }^{+}{\nu }_{\tau })/\mathcal{B}(B_c^{+}\to J/\psi {\mu }^{+}{\nu }_{\mu })$, where the ${\tau }^{+}$ lepton is identified in the decay mode ${\tau }^{+}\to {\mu }^{+}{\nu }_{\mu }{\overline{\nu }}_{\tau }$. This analysis uses a sample of proton-proton collision data corresponding to $3.0{\mathrm{fb}}^{-1}$ of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay $B_c^{+}\to J/\psi {\tau }^{+}{\nu }_{\tau }$ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be $\mathcal{R}(J/\psi )=0.71\pm 0.17(\mathrm{stat})\pm 0.18(\mathrm{syst})$. This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.

The transverse momentum spectra of weak gauge bosons and their ratios probe the underlying dynamics and are crucial in testing our understanding of the standard model. They are an essential ingredient in precision measurements, such as the $W$ boson mass extraction. To fully exploit the potential of the LHC data, we compute the second-order [next-to-next-to-leading-order (NNLO)] QCD corrections to the inclusive-$p_T^W$ spectrum as well as to the ratios of spectra for $W^{-}/W^{+}$ and $Z/W$. We find that the inclusion of NNLO QCD corrections considerably improves the theoretical description of the experimental CMS data and results in a substantial reduction of the residual scale uncertainties.

A beam containing a substantial component of both the $J^{\pi }=5^{+}$, $T_{1/2}=162\mathrm{ns}$ isomeric state of ${}^{18}\mathrm{F}$ and its $1^{+}$, 109.77-min ground state is utilized to study members of the ground-state rotational band in ${}^{19}\mathrm{F}$ through the neutron transfer reaction ($d$,$p$) in inverse kinematics. The resulting spectroscopic strengths confirm the single-particle nature of the $13/2^{+}$ band-terminating state. The agreement between shell-model calculations using an interaction constructed within the $sd$ shell, and our experimental results reinforces the idea of a single-particle–collective duality in the descriptions of the structure of atomic nuclei.

With dielectric-constant gas thermometry, the molar polarizability of helium, neon, and argon has been determined with relative standard uncertainties of about 2 parts per million. A series of isotherms measured with the three noble gases and two different experimental setups led to this unprecedented level of uncertainty. These data are crucial for scientists in the field of gas metrology, working on pressure and temperature standards. Furthermore, with the new benchmark values for neon and argon, theoretical calculations, today about 3 orders of magnitude larger in uncertainty, can be checked and improved.

An array of single Rydberg atoms driven by a temporally modulated atom-field detuning is studied. The periodic modulation effectively modifies the Rabi coupling, leading to unprecedented dynamics in the presence of Rydberg-Rydberg interactions, in particular, blockade enhancement, antiblockades, and state-dependent population trapping. Interestingly, the Schrieffer-Wolf transformation reveals a fundamental process in Rydberg gases, correlated Rabi coupling, which stems from the extended nature of the Rydberg-Rydberg interactions. Also, the correlated coupling provides an alternative depiction for the Rydberg blockade, exhibiting a nontrivial behavior in the presence of periodic modulation. The dynamical localization of a many-body configuration in a driven Rydberg lattice is discussed.

Supersolids are characterized by the counterintuitive coexistence of superfluid and crystalline order. Here we study a supersolid phase emerging in the steady state of a driven-dissipative system. We consider a transversely pumped Bose-Einstein condensate trapped along the axis of a ring cavity and coherently coupled to a pair of degenerate counterpropagating cavity modes. Above a threshold pump strength the interference of photons scattered into the two cavity modes results in an emergent superradiant lattice, which spontaneously breaks the continuous translational symmetry towards a periodic atomic pattern. The crystalline steady state inherits the superfluidity of the Bose-Einstein condensate, thus exhibiting genuine properties of a supersolid. A gapless collective Goldstone mode correspondingly appears in the superradiant phase, which can be nondestructively monitored via the relative phase of the two cavity modes on the cavity output. Despite cavity-photon losses the Goldstone mode remains undamped, indicating the robustness of the supersolid phase.

We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to a chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical systems but here in a relativistic quantum setting—henceforth the term “Dirac quantum chimera,” associated with which are physical phenomena with potentially significant applications such as enhancement of spin polarization, unusual coexisting quasibound states for distinct spin configurations, and spin selective caustics. Experimental observations of these phenomena are possible through, e.g., optical realizations of ballistic Dirac fermion systems.

Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, and measured with another 20 GeV lower charge trailing positron probe bunch. The measurements are largely consistent with theory.

The impact of the carrier-envelope phase (CEP) of an intense multicycle laser pulse on the radiation of an electron beam during nonlinear Compton scattering is investigated. We have identified a CEP effect specific to the ultrarelativistic regime. When the electron beam counterpropagates with the laser pulse, pronounced high-energy x-ray double peaks emerge near the backward direction relative to the initial electron motion. This is achieved in the relativistic interaction domain, where both the electron energy is required to be lower than for the electron reflection condition at the laser peak and the stochasticity effects in the photon emission need to be weak. The asymmetry parameter of the double peaks in the angular radiation distribution is shown to serve as a sensitive measure for the CEP of up to 10-cycle long laser pulses and can be applied for the characterization of extremely strong laser pulses in present and near future laser facilities.

Multiple self-emission x-ray images are used to measure tomographically target modes 1, 2, and 3 up to the end of the target acceleration in direct-drive implosions on OMEGA. Results show that the modes consist of two components: the first varies linearly with the laser beam-energy balance and the second is static and results from physical effects including beam mistiming, mispointing, and uncertainty in beam energies. This is used to reduce the target low modes of low-adiabat implosions from 2.2% to 0.8% by adjusting the beam-energy balance to compensate these static modes.

Pt-Rh alloy nanoparticles on oxide supports are widely employed in heterogeneous catalysis with applications ranging from automotive exhaust control to energy conversion. To improve catalyst performance, an atomic-scale correlation of the nanoparticle surface structure with its catalytic activity under industrially relevant operando conditions is essential. Here, we present x-ray diffraction data sensitive to the nanoparticle surface structure combined with in situ mass spectrometry during near ambient pressure CO oxidation. We identify the formation of ultrathin surface oxides by detecting x-ray diffraction signals from particular nanoparticle facets and correlate their evolution with the sample’s enhanced catalytic activity. Our approach opens the door for an in-depth characterization of well-defined, oxide-supported nanoparticle based catalysts under operando conditions with unprecedented atomic-scale resolution.

We investigate the interplay of spin-orbit coupling (SOC) and electronic correlations in ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ using dynamical mean-field theory. We find that SOC does not affect the correlation-induced renormalizations, which validates Hund’s metal picture of ruthenates even in the presence of the sizable SOC relevant to these materials. Nonetheless, SOC is found to change significantly the electronic structure at $k$ points where a degeneracy applies in its absence. We explain why these two observations are consistent with one another and calculate the effects of SOC on the correlated electronic structure. The magnitude of these effects is found to depend on the energy of the quasiparticle state under consideration, leading us to introduce the notion of an energy-dependent quasiparticle spin-orbit coupling ${\lambda }^{*}(\omega )$. This notion is generally applicable to all materials in which both the spin-orbit coupling and electronic correlations are sizable.

We study the higher-order Fermi-liquid relations of Kondo systems for arbitrary impurity-electron fillings, extending the many-body quantum theoretical approach of Yamada and Yosida. It includes, partly, a microscopic clarification of the related achievements based on Nozières’ phenomenological description: Filippone, Moca, von Delft, and Mora [Phys. Rev. B 95, 165404 (2017)]. In our formulation, the Fermi-liquid parameters such as the quasiparticle energy, damping, and transport coefficients are related to each other through the total vertex ${\mathrm{\Gamma }}_{\sigma {\sigma }^{\prime };{\sigma }^{\prime }\sigma }(\omega ,{\omega }^{\prime };{\omega }^{\prime },\omega )$, which may be regarded as a generalized Landau quasiparticle interaction. We obtain exactly this function up to linear order with respect to the frequencies $\omega$ and ${\omega }^{\prime }$ using the antisymmetry and analytic properties. The coefficients acquire additional contributions of three-body fluctuations away from half filling through the nonlinear susceptibilities. We also apply the formulation to nonequilibrium transport through a quantum dot, and clarify how the zero-bias peak evolves in a magnetic field.

We investigate yttrium iron garnet (YIG)/cobalt (Co) heterostructures using broadband ferromagnetic resonance (FMR). We observe an efficient excitation of perpendicular standing spin waves (PSSWs) in the YIG layer when the resonance frequencies of the YIG PSSWs and the Co FMR line coincide. Avoided crossings of YIG PSSWs and the Co FMR line are found and modeled using mutual spin pumping and exchange torques. The excitation of PSSWs is suppressed by a thin aluminum oxide interlayer but persists with a copper interlayer, in agreement with the proposed model.