86,073 research outputs found
Inelastic Effects in Low-Energy Electron Reflectivity of Two-dimensional Materials
A simple method is proposed for inclusion of inelastic effects (electron
absorption) in computations of low-energy electron reflectivity (LEER) spectra.
The theoretical spectra are formulated by matching of electron wavefunctions
obtained from first-principles computations in a repeated vacuum-slab-vacuum
geometry. Inelastic effects are included by allowing these states to decay in
time in accordance with an imaginary term in the potential of the slab, and by
mixing of the slab states in accordance with the same type of distribution as
occurs in a free-electron model. LEER spectra are computed for various
two-dimensional materials, including free-standing multilayer graphene,
graphene on copper substrates, and hexagonal boron nitride (h-BN) on cobalt
substrates.Comment: 21 pages, 7 figure
Optimal Controlled Teleportation
We give the analytic expressions of maximal probabilities of successfully
controlled teleportating an unknown qubit via every kind of tripartite states.
Besides, another kind of localizable entanglement is also determined.
Furthermore, we give the sufficient and necessary condition that a three-qubit
state can be collapsed to an EPR pair by a measurement on one qubit, and
characterize the three-qubit states that can be used as quantum channel for
controlled teleporting a qubit of unknown information with unit probability and
with unit fidelity.Comment: 4 page
Bose-Einstein condensates in RF-dressed adiabatic potentials
Bose-Einstein condensates of Rb atoms are transferred into
radio-frequency (RF) induced adiabatic potentials and the properties of the
corresponding dressed states are explored. We report on measurements of the
spin composition of dressed condensates. We also show that adiabatic potentials
can be used to trap atom gases in novel geometries, including suspending a
cigar-shaped cloud above a curved sheet of atoms
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Tuning magnetic anisotropy of epitaxial Ag/Fe/Fe0.5Co0.5/MgO(001) films
Single crystalline Ag/Fe/Fe0.5Co0.5/MgO(001) films were grown by Molecular Beam Epitaxy and investigated by Magneto-Optic Kerr Effect (MOKE). We find that even though the 4-fold magnetic anisotropies of Ag/Fe/MgO(001) and Ag/Fe0.5Co0.5/MgO(001) films are different from the corresponding bulk values, their opposite signs allow a fine tuning of the 4-fold magnetic anisotropy in Ag/Fe/Fe0.5Co0.5/MgO(001) films by varying the Fe and Fe0.5Co0.5 film thicknesses. In particular, the critical point of zero anisotropy can be achieved in a wide range of film thicknesses. Using Rotational MOKE, we determined and constructed the anisotropy phase diagram in the Fe and Fe0.5Co0.5 thickness plane from which the zero anisotropy exhibits a linear relation between the Fe and Fe0.5Co0.5 thickness
Forward-backward asymmetry of photoemission in C excited by few-cycle laser pulses
We theoretically analyze angle-resolved photo-electron spectra (ARPES)
generated by the interaction of C with intense, short laser pulses. In
particular, we focus on the impact of the carrier-envelope phase (CEP) onto the
angular distribution. The electronic dynamics is described by time-dependent
density functional theory, and the ionic background of \csixty is
approximated by a particularly designed jellium model. Our results show a clear
dependence of the angular distributions onto the CEP for very short pulses
covering only very few laser cycles, which disappears for longer pulses. For
the specific laser parameters used in a recent experiments, a very good
agreement is obtained. Furthermore, the asymmetry is found to depend on the
energy of the emitted photoelectrons. The strong influence of the angular
asymmetry of electron emission onto the CEP and pulse duration suggests to use
this sensitivity as a means to analyze the structure of few-cycle laser pulses.Comment: 8 pages, 6 figure
Effective potentials for atom-atom interaction at low temperatures
We discuss the concept and design of effective atom-atom potentials that
accurately describe any physical processes involving only states around the
threshold. The existence of such potentials gives hope to a quantitative, and
systematic, understanding of quantum few-atom and quantum many-atom systems at
relatively low temperatures.Comment: 4 pages, 4 figure
Multi-GeV Neutrino Emission from Magnetized Gamma Ray Bursts
We investigate the expected neutrino emissivity from nuclear collisions in
magnetically dominated collisional models of gamma-ray bursts, motivated by
recent observational and theoretical developments. The results indicate that
significant multi-GeV neutrino fluxes are expected for model parameter values
which are typical of electromagnetically detected bursts. We show that for
detecting at least one muon event in Icecube and its Deep Core sub-array, a
single burst must be near the high end of the luminosity function and at a
redshift . We also calculate the luminosity and distance ranges
that can generate muon events per GRB in the same detectors, which may
be of interest if simultaneously detected electromagnetically, or if measured
with future extensions of Icecube or other neutrino detectors with larger
effective volume and better sensitivity.Comment: 12 pages, 7 figures, accepted version for Phys.Rev.
An approach to exact solutions of the time-dependent supersymmetric two-level three-photon Jaynes-Cummings model
By utilizing the property of the supersymmetric structure in the two-level
multiphoton Jaynes-Cummings model, an invariant is constructed in terms of the
supersymmetric generators by working in the sub-Hilbert-space corresponding to
a particular eigenvalue of the conserved supersymmetric generators. We obtain
the exact solutions of the time-dependent Schr\"{o}dinger equation which
describes the time-dependent supersymmetric two-level three-photon
Jaynes-Cummings model (TLTJCM) by using the invariant-related unitary
transformation formulation. The case under the adiabatic approximation is also
discussed.
Keywords: Supersymmetric Jaynes-Cummings model; exact solutions; invariant
theory; geometric phase factor; adiabatic approximationComment: 7 pages, Late
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