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Physical Review Letters

L-J Chen, S Wang, L B Wilson, S Schwartz, N Bessho, T Moore, D Gershman, B Giles, D Malaspina, F D Wilder, R E Ergun, M Hesse, H Lai, C Russell, R Strangeway, R B Torbert, A F-Vinas, J Burch, S Lee, C Pollock, J Dorelli, W Paterson, N Ahmadi, K Goodrich, B Lavraud, O Le Contel, Yu V Khotyaintsev, P-A Lindqvist, S Boardsen, H Wei, A Le, L Avanov
Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed...
June 1, 2018: Physical Review Letters
J G Vale, S Calder, C Donnerer, D Pincini, Y G Shi, Y Tsujimoto, K Yamaura, M Moretti Sala, J van den Brink, A D Christianson, D F McMorrow
The temperature dependence of the excitation spectrum in NaOsO_{3} through its metal-to-insulator transition (MIT) at 410 K has been investigated using resonant inelastic x-ray scattering at the Os L_{3} edge. High-resolution (ΔE∼56  meV) measurements show that the well-defined, low-energy magnons in the insulating state weaken and dampen upon approaching the metallic state. Concomitantly, a broad continuum of excitations develops which is well described by the magnetic fluctuations of a nearly antiferromagnetic Fermi liquid...
June 1, 2018: Physical Review Letters
D Turnbull, P Franke, J Katz, J P Palastro, I A Begishev, R Boni, J Bromage, A L Milder, J L Shaw, D H Froula
Flying focus is a technique that uses a chirped laser beam focused by a highly chromatic lens to produce an extended focal region within which the peak laser intensity can propagate at any velocity. When that intensity is high enough to ionize a background gas, an ionization wave will track the intensity isosurface corresponding to the ionization threshold. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced that propagated both forward and backward relative to the ionizing laser...
June 1, 2018: Physical Review Letters
Bob Holdom, Jing Ren, Chen Zhang
If quark matter is energetically favored over nuclear matter at zero temperature and pressure, then it has long been expected to take the form of strange quark matter (SQM), with comparable amounts of u, d, and s quarks. The possibility of quark matter with only u and d quarks (udQM) is usually dismissed because of the observed stability of ordinary nuclei. However, we find that udQM generally has lower bulk energy per baryon than normal nuclei and SQM. This emerges in a phenomenological model that describes the spectra of the lightest pseudoscalar and scalar meson nonets...
June 1, 2018: Physical Review Letters
P S Bhupal Dev, Rabindra N Mohapatra, Yongchao Zhang
Many new physics scenarios beyond standard model often necessitate the existence of a (light) neutral scalar H, which might couple to the charged leptons in a flavor violating way, while evading all existing constraints. We show that such scalars could be effectively produced at future lepton colliders, either on shell or off shell depending on their mass, and induce lepton flavor violating (LFV) signals, i.e., e^{+}e^{-}→ℓ_{α}^{±}ℓ_{β}^{∓}(+H) with α≠β. We find that a large parameter space of the scalar mass and the LFV couplings can be probed well beyond the current low-energy constraints in the lepton sector...
June 1, 2018: Physical Review Letters
P Wirnsberger, C Dellago, D Frenkel, A Reinhardt
We present a mean-field theory to explain the thermo-orientation effect in an off-center Stockmayer fluid. This effect is the underlying cause of thermally induced polarization and thermally induced monopoles, which have recently been predicted theoretically. Unlike previous theories that are based either on phenomenological equations or on scaling arguments, our approach does not require any fitting parameters. Given an equation of state and assuming local equilibrium, we construct an effective Hamiltonian for the computation of local Boltzmann averages...
June 1, 2018: Physical Review Letters
F Tsitoura, U Gietz, A Chabchoub, N Hoffmann
We report a theoretical derivation, an experimental observation and a numerical validation of nonlinear phase domain walls in weakly nonlinear deep water surface gravity waves. The domain walls presented are connecting homogeneous zones of weakly nonlinear plane Stokes waves of identical amplitude and wave vector but differences in phase. By exploiting symmetry transformations within the framework of the nonlinear Schrödinger equation we demonstrate the existence of exact analytical solutions representing such domain walls in the weakly nonlinear limit...
June 1, 2018: Physical Review Letters
Takashi Ishii, Tomotaka Kuwahara, Takashi Mori, Naomichi Hatano
We investigate a heating phenomenon in periodically driven integrable systems that can be mapped to free-fermion models. We find that heating to the high-temperature state, which is a typical scenario in nonintegrable systems, can also appear in integrable time-periodic systems; the amount of energy absorption rises drastically near a frequency threshold where the Floquet-Magnus expansion diverges. As the driving period increases, we also observe that the effective temperatures of the generalized Gibbs ensemble for conserved quantities go to infinity...
June 1, 2018: Physical Review Letters
R Fridström, B E Chapman, A F Almagri, L Frassinetti, P R Brunsell, T Nishizawa, J S Sarff
In a magnetically confined plasma with a stochastic magnetic field, the dependence of the perpendicular viscosity on the magnetic fluctuation amplitude is measured for the first time. With a controlled, ∼ tenfold variation in the fluctuation amplitude, the viscosity increases ∼100-fold, exhibiting the same fluctuation-amplitude-squared dependence as the predicted rate of stochastic field line diffusion. The absolute value of the viscosity is well predicted by a model based on momentum transport in a stochastic field, the first in-depth test of this model...
June 1, 2018: Physical Review Letters
M Hamoumi, P E Allain, W Hease, E Gil-Santos, L Morgenroth, B Gérard, A Lemaître, G Leo, I Favero
We report on a systematic study of nanomechanical dissipation in high-frequency (≈300  MHz) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties...
June 1, 2018: Physical Review Letters
Aleš Hrabec, Viola Křižáková, Stefania Pizzini, João Sampaio, André Thiaville, Stanislas Rohart, Jan Vogel
Magnetic domain walls are objects whose dynamics is inseparably connected to their structure. In this Letter, we investigate magnetic bilayers, which are engineered such that a coupled pair of domain walls, one in each layer, is stabilized by a cooperation of Dzyaloshinskii-Moriya interaction and flux-closing mechanism. The dipolar field mediating the interaction between the two domain walls links not only their position but also their structure. We show that this link has a direct impact on their magnetic-field-induced dynamics...
June 1, 2018: Physical Review Letters
C Ravensbergen, V Corre, E Soave, M Kreyer, S Tzanova, E Kirilov, R Grimm
We report a measurement of the dynamical polarizability of dysprosium atoms in their electronic ground state at the optical wavelength of 1064 nm, which is of particular interest for laser trapping experiments. Our method is based on collective oscillations in an optical dipole trap, and reaches unprecedented accuracy and precision by comparison with an alkali atom (potassium) as a reference species. We obtain values of 184.4(2.4) and 1.7(6) a.u. for the scalar and tensor polarizability, respectively. Our experiments have reached a level that permits meaningful tests of current theoretical descriptions and provides valuable information for future experiments utilizing the intriguing properties of heavy lanthanide atoms...
June 1, 2018: Physical Review Letters
Sam Dillavou, Shmuel M Rubinstein
We measure the static frictional resistance and the real area of contact between two solid blocks subjected to a normal load. We show that following a two-step change in the normal load the system exhibits nonmonotonic aging and memory effects, two hallmarks of glassy dynamics. These dynamics are strongly influenced by the discrete geometry of the frictional interface, characterized by the attachment and detachment of unique microcontacts. The results are in good agreement with a theoretical model we propose that incorporates this geometry into the framework recently used to describe Kovacs-like relaxation in glasses as well as thermal disordered systems...
June 1, 2018: Physical Review Letters
James T Liu, Leopoldo A Pando Zayas, Vimal Rathee, Wenli Zhao
Within 11-dimensional supergravity we compute the logarithmic correction to the entropy of magnetically charged asymptotically AdS_{4} black holes with arbitrary horizon topology. We find perfect agreement with the expected microscopic result arising from the dual field theory computation of the topologically twisted index. Our result relies crucially on a particular limit to the extremal black hole case and clarifies some aspects of quantum corrections in asymptotically AdS spacetimes.
June 1, 2018: Physical Review Letters
Cosmo Lupo, Carlo Ottaviani, Panagiotis Papanastasiou, Stefano Pirandola
One crucial step in any quantum key distribution (QKD) scheme is parameter estimation. In a typical QKD protocol the users have to sacrifice part of their raw data to estimate the parameters of the communication channel as, for example, the error rate. This introduces a trade-off between the secret key rate and the accuracy of parameter estimation in the finite-size regime. Here we show that continuous-variable QKD is not subject to this constraint as the whole raw keys can be used for both parameter estimation and secret key generation, without compromising the security...
June 1, 2018: Physical Review Letters
R Gran, M Betancourt, M Elkins, P A Rodrigues, F Akbar, L Aliaga, D A Andrade, A Bashyal, L Bellantoni, A Bercellie, A Bodek, A Bravar, H Budd, G F R Caceres Vera, T Cai, M F Carneiro, D Coplowe, H da Motta, S A Dytman, G A Díaz, J Felix, L Fields, R Fine, H Gallagher, A Ghosh, H Haider, J Y Han, D A Harris, S Henry, D Jena, J Kleykamp, M Kordosky, T Le, J R Leistico, A Lovlein, X-G Lu, E Maher, S Manly, W A Mann, C M Marshall, K S McFarland, A M McGowan, B Messerly, J Miller, A Mislivec, J G Morfín, J Mousseau, D Naples, J K Nelson, C Nguyen, A Norrick, Nuruzzaman, A Olivier, V Paolone, C E Patrick, G N Perdue, M A Ramírez, R D Ransome, H Ray, L Ren, D Rimal, D Ruterbories, H Schellman, C J Solano Salinas, H Su, M Sultana, S Sánchez Falero, E Valencia, J Wolcott, M Wospakrik, B Yaeggy
We report on multinucleon effects in low momentum transfer (<0.8  GeV/c) antineutrino interactions on plastic (CH) scintillator. These data are from the 2010-2011 antineutrino phase of the MINERvA experiment at Fermilab. The hadronic energy spectrum of this inclusive sample is well described when a screening effect at a low energy transfer and a two-nucleon knockout process are added to a relativistic Fermi gas model of quasielastic, Δ resonance, and higher resonance processes. In this analysis, model elements introduced to describe previously published neutrino results have quantitatively similar benefits for this antineutrino sample...
June 1, 2018: Physical Review Letters
Lachlan P Lindoy, David E Manolopoulos
We describe a simple quantum mechanical method that can be used to obtain accurate numerical results over long timescales for the spin correlation tensor of an electron spin that is hyperfine coupled to a large number of nuclear spins. This method does not suffer from the statistical errors that accompany a Monte Carlo sampling of the exact eigenstates of the central spin Hamiltonian obtained from the algebraic Bethe ansatz, or from the growth of the truncation error with time in the time-dependent density matrix renormalization group (TDMRG) approach...
June 1, 2018: Physical Review Letters
Jianxiong Li, Erfan Saydanzad, Uwe Thumm
We propose a scheme for the reconstruction of plasmonic near fields at isolated nanoparticles from infrared-streaked extreme-ultraviolet photoemission spectra. Based on quantum-mechanically modeled spectra, we demonstrate and analyze the accurate imaging of the IR-streaking-pulse-induced transient plasmonic fields at the surface of gold nanospheres and nanoshells with subfemtosecond temporal and subnanometer spatial resolution.
June 1, 2018: Physical Review Letters
Liang Li, Pengfei Lan, Lixin He, Xiaosong Zhu, Jing Chen, Peixiang Lu
A photon channel perspective on high harmonic generation (HHG) is proposed by quantizing both the driving laser and high harmonics. It is shown that the HHG yield can be expressed as a sum of the contribution of all the photon channels. From this perspective, the contribution of a specific photon channel follows a simple scaling law and the competition between the channels is well interpreted. Our prediction is shown to be in good agreement with the simulations by solving the time-dependent Schrödinger equation...
June 1, 2018: Physical Review Letters
Samuel D McDermott
We suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v^{n}∼(10^{-(2-3)})^{n}, where n=1, 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ∼0...
June 1, 2018: Physical Review Letters
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