This Letter presents a search for $tb$ resonances in $1.04{\mathrm{fb}}^{-1}$ of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the $tb$ invariant mass distribution compared to the expected standard model backgrounds. The model of a right-handed $W_R^{\prime }$ with standard model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in the data, and upper limits on the cross section times the branching ratio of $W_R^{\prime }$ resonances at 95% C.L. lie in the range of 6.1–1.0 pb for $W_R^{\prime }$ masses ranging from 0.5 to 2.0 TeV. These limits are translated into a lower bound on the allowed right-handed $W_R^{\prime }$ mass, giving $m_{W_R^{\prime }}>1.13\mathrm{TeV}$ at 95% C.L.

We present an ellipticity-resolved study of momentum distributions arising from strong-field ionization of helium. The influence of the ion potential on the departing electron is considered within a semiclassical model consisting of an initial tunneling step and subsequent classical propagation. We find that the momentum distribution can be explained by including the longitudinal momentum spread of the electron at the exit from the tunnel. Our combined experimental and theoretical study provides an estimate of this momentum spread.

We report experiments on lateral migration of bubbles in a two-dimensional foam sheared in a narrow-gap Couette device. A larger bubble in an otherwise monodisperse bubble raft migrates toward the center of the gap as long as the bubble size ratio and the shear rate are each above a threshold. The migration speed is roughly two orders of magnitude higher than that of a single bubble, and increases with the shear rate and the size ratio. The bubble also deforms much more than an isolated one at the same shear rate. Modifying the Chan–Leal solution for the migration of a single submerged bubble or drop, we derive a formula that successfully predicts all the migration trajectories recorded in the experiment. The threshold for migration corresponds to the wall repulsion force overcoming the capillary force in the two-dimensional foam. The size-differentiated bubble migration provides an explanation for previously observed size segregation in sheared three-dimensional polydisperse foams.

We investigate the relative phase between two weakly interacting 1D condensates of bosonic atoms after suddenly switching on the tunnel coupling. The following phase dynamics is governed by the quantum sine-Gordon equation. In the semiclassical limit of weak interactions, we observe the parametric amplification of quantum fluctuations leading to the formation of breathers with a finite lifetime. The typical lifetime and density of these “quasibreathers” are derived employing exact solutions of the classical sine-Gordon equation. Both depend on the initial relative phase between the condensates, which is considered as a tunable parameter.

Without the availability of slip systems and dislocation glide as in crystalline materials, metallic glasses resist irreversible deformation to elastic strains of 2% or more before undergoing heterogeneous plastic flow via the formation of shear bands. Observation of crystallite formation under compressive load was previously obtained by transmission electron microscopy. In this Letter, we present results of nondestructive x-ray diffraction microprofiling of the section of a bent glassy ${\mathrm{Pd}}_{40}{\mathrm{Cu}}_{30}{\mathrm{Ni}}_{10}{\mathrm{P}}_{20}$ ribbon in transmission using a synchrotron microbeam. Crystallization was clearly detected but only on the compression side of the neutral fiber. The experimental results and crystal nucleation frequency analysis are consistent with massive nucleation in shear bands forming under compressive stress but mainly for metallic glasses that show a large supercooled liquid temperature range $\Delta T=T_x-T_g$ between glass transition at $T_g$ and crystallization at $T_x$. The phenomenon is sensitively dependent on the volume change that accompanies crystallization in the supercooled liquid temperature range where the much larger liquid-state thermal expansion coefficient significantly increases the specific volume difference between the liquid and crystalline states. The results are also consistent with the many reports of extensive strain to fracture of metallic glasses under compressive load but not under tension.

The insulator-metal transition was observed experimentally in nickel monoxide (NiO) at very high pressures of $\sim 240\mathrm{GPa}$. The sample resistance becomes measurable at about 130 GPa and decreases substantially with the pressure increase to $\sim 240\mathrm{GPa}$. A sharp drop in resistance by about 3 orders of magnitude has been observed at $\sim 240\mathrm{GPa}$ with a concomitant change of the resistance type from semiconducting to metallic. This is the first experimental observation of an insulator-metal transition in NiO, which was anticipated by Mott decades ago. From simple multielectron consideration, the metallic phase of NiO forms when the effective Hubbard energy $U_{\mathrm{eff}}$ is almost equal to the estimated full bandwidth $2W$.

We present nuclear spin relaxation measurements in GaAs epilayers using a new pump-probe technique in all-electrical, lateral spin-valve devices. The measured $T_1$ times agree very well with NMR data available for $T>1\mathrm{K}$. However, the nuclear spin relaxation rate clearly deviates from the well-established Korringa law expected in metallic samples and follows a sublinear temperature dependence $T_1^{-1}\propto T^{0.6}$ for $0.1\mathrm{K}\le T\le 10\mathrm{K}$. Further, we investigate nuclear spin inhomogeneities.

The thermal conductivity $\kappa$ of the iron arsenide superconductor ${\mathrm{KFe}}_2{\mathrm{As}}_2$ was measured down to 50 mK for a heat current parallel and perpendicular to the tetragonal $c$ axis. A residual linear term at $T\to 0$, ${\kappa }_0/T$ is observed for both current directions, confirming the presence of nodes in the superconducting gap. Our value of ${\kappa }_0/T$ in the plane is equal to that reported by Dong et al. [Phys. Rev. Lett. 104, 087005 (2010)] for a sample whose residual resistivity ${\rho }_0$ was 10 times larger. This independence of ${\kappa }_0/T$ on impurity scattering is the signature of universal heat transport, a property of superconducting states with symmetry-imposed line nodes. This argues against an $s$-wave state with accidental nodes. It favors instead a $d$-wave state, an assignment consistent with five additional properties: the magnitude of the critical scattering rate ${\Gamma }_c$ for suppressing $T_c$ to zero; the magnitude of ${\kappa }_0/T$, and its dependence on current direction and on magnetic field; the temperature dependence of $\kappa (T)$.

The superconducting compound LiFeAs is studied by scanning tunneling microscopy and spectroscopy. A gap map of the unreconstructed surface indicates a high degree of homogeneity in this system. Spectra at 2 K show two nodeless superconducting gaps with ${\Delta }_1=5.3\pm 0.1\mathrm{meV}$ and ${\Delta }_2=2.5\pm 0.2\mathrm{meV}$. The gaps close as the temperature is increased to the bulk $T_c$, indicating that the surface accurately represents the bulk. A dip-hump structure is observed below $T_c$ with an energy scale consistent with a magnetic resonance recently reported by inelastic neutron scattering.

We have studied frustrated kagome arrays and unfrustrated honeycomb arrays of magnetostatically interacting single-domain ferromagnetic islands with magnetization normal to the plane. The measured pairwise spin correlations of both lattices can be reproduced by models based solely on nearest-neighbor correlations. The kagome array has qualitatively different magnetostatics but identical lattice topology to previously studied artificial spin ice systems composed of in-plane moments. The two systems show striking similarities in the development of moment pair correlations, demonstrating a universality in artificial spin ice behavior independent of specific realization in a particular material system.

We present a theoretical study of magnon-mediated heat transport in electrically insulating ferromagnetic wires containing a domain wall (DW). In the regime of validity of continuum micromagnetism, a DW is found to have no effect on the heat conductance. However, spin waves are found to be reflected by DWs with widths of a few lattice spacings, which is associated with emergence of an additional spin wave bound state. The resulting DW heat conductance should be significant for thin films of yttrium iron garnet with sharply defined magnetic domains.

The crossover region in the phase diagram of polymer solutions, in the regime above the overlap concentration, is explored by Brownian dynamics simulations to map out the universal crossover scaling functions for the gyration radius and the single-chain diffusion constant. Scaling considerations, our simulation results, and recently reported data on the polymer contribution to the viscosity obtained from rheological measurements on DNA systems support the assumption that there are simple relations between these functions, such that they can be inferred from one another.

The first passage time (FPT) for random walks is a key indicator of how fast information diffuses in a given system. Despite the role of FPT as a fundamental feature in transport phenomena, its behavior, particularly in heterogeneous networks, is not yet fully understood. Here, we study, both analytically and numerically, the scaling behavior of the FPT distribution to a given target node, averaged over all starting nodes. We find that random walks arrive quickly at a local hub, and therefore, the FPT distribution shows a crossover with respect to time from fast decay behavior (induced from the attractive effect to the hub) to slow decay behavior (caused by the exploring of the entire system). Moreover, the mean FPT is independent of the degree of the target node in the case of compact exploration. These theoretical results justify the necessity of using a random jump protocol (empirically used in search engines) and provide guidelines for designing an effective network to make information quickly accessible.

It is well known that increasing the nonlinearity due to repulsive atomic interactions in a double-well Bose-Einstein condensate suppresses quantum tunneling between the two sites. Here we find analogous behavior in the dynamical tunneling of a Bose-Einstein condensate between period-one resonances in a single driven potential well. For small nonlinearities we find unhindered tunneling between the resonances, but with an increasing period as compared to the noninteracting system. For nonlinearities above a critical value we generally observe that the tunneling shuts down. However, for certain regimes of modulation parameters we find that dynamical tunneling reemerges for large enough nonlinearities, an effect not present in spatial double-well tunneling. We develop a two-mode model in good agreement with full numerical simulations over a wide range of parameters, which allows the suppression of tunneling to be attributed to macroscopic quantum self-trapping.

We realize fast transport of ions in a segmented microstructured Paul trap. The ion is shuttled over a distance of more than ${10}^4$ times its ground state wave function size during only five motional cycles of the trap ($280\mu \mathrm{m}$ in $3.6\mu \mathrm{s}$). Starting from a ground-state-cooled ion, we find an optimized transport such that the energy increase is as low as $0.10\pm 0.01$ motional quanta. In addition, we demonstrate that quantum information stored in a spin-motion entangled state is preserved throughout the transport. Shuttling operations are concatenated, as a proof-of-principle for the shuttling-based architecture to scalable ion trap quantum computing.

We investigate the dynamics of single and multiple ions during transport between and separation into spatially distinct locations in a multizone linear Paul trap. A single ${}^9\mathrm{Be}^{+}$ ion in a $\sim 2\mathrm{MHz}$ harmonic well was transported $370\mu \mathrm{m}$ in $8\mu \mathrm{s}$, corresponding to 16 periods of oscillation, with a gain of 0.1 motional quanta. Similar results were achieved for the transport of two ions. We also separated chains of up to 9 ions from one potential well to two distinct potential wells. With two ions this was accomplished in $55\mu \mathrm{s}$, with excitations of approximately two quanta for each ion. Fast transport and separation can significantly reduce the time overhead in certain architectures for scalable quantum information processing with trapped ions.

In this paper we present in situ satellite data, theory, and laboratory validation that show how small-scale collisionless shocks and minimagnetospheres can form on the electron inertial scale length. The resulting retardation and deflection of the solar wind ions could be responsible for the unusual “lunar swirl” patterns seen on the surface of the Moon.

We show that anti–de Sitter/quantum chromodynamics generates predictions for the rate of diffractive $\rho$-meson electroproduction that are in agreement with data collected at the Hadron Electron Ring Accelerator electron–proton collider.

We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train.

We consider a uniform superfluid confined in two compartments connected by a superleak and initially held at equal temperatures. If one of the two compartments is heated, a fraction of the superfluid will flow through the superleak. We show that, under certain thermodynamic conditions, the atoms flow from the hotter to the colder compartment, contrary to what happens in the fountain effect observed in superfluid helium. This flow causes quantum degeneracy to increase in the colder compartment. In superfluid helium, this novel thermomechanical effect takes place in the phonon regime of very low temperatures. In dilute quantum gases, it occurs at all temperatures below $T_c$. The increase in quantum degeneracy reachable through the adiabatic displacement of the wall separating the two compartments is also discussed.