218 research outputs found
Electrodynamic trapping of spinless neutral atoms with an atom chip
Three dimensional electrodynamic trapping of neutral atoms has been
demonstrated. By applying time-varying inhomogeneous electric fields with
micron-sized electrodes, nearly strontium atoms in the state
have been trapped with a lifetime of 80 ms. In order to design the electrodes,
we numerically analyzed the electric field and simulated atomic trajectories in
the trap, which showed reasonable agreement with the experiment.Comment: 4pages, 4figures, to appear in Phys. Rev. Let
Strong Anisotropy in Spin Suceptibility of Superfluid 3He-B Film Caused by Surface Bound States
Spin susceptibility of superfluid 3He-B film with specular surfaces is
calculated. It is shown that, when the magnetic field is applied in a direction
perpendiculr to the film, the suseptibility is significantly enhanced by the
contribution from the surface bound states. No such enhancement is found for
the magnetic field parallel to the film. A simplified model with spatially
constant order parameter is used to elucidate the magnetic properties of the
surface bound states. The Majorana nature of the zero energy bound state is
also mentioned.Comment: 4 pages, 4 figure
Quasiclassical theory of superconductivity: a multiple interface geometry
The purpose of the paper is to suggest a new method which allows one to study
multiple coherent reflection/transmissions by partially transparent interfaces
(e.g. in multi-layer mesoscopic structures or grain boundaries in high-Tc's) in
the framework of the quasiclassical theory of superconductivity. It is argued
that typically the trajectory of the particle is a simply connected tree (no
loops) with knots, i.e. the points where interface scattering events occur and
ballistic pieces of the trajectory are mixed. A linear boundary condition for
the 2-component trajectory "wave function" which factorizes matrix (retarded)
Green's function, is formulated for an arbitrary interface, specular or
diffusive. To show the usage of the method, the current response to the vector
potential (the total superfluid density rho_s) of a SS' sandwich with the
different signs of the order parameter in S and S', is calculated. In this
model, a few percent of reflection by the SS' interface transforms the
paramagnetic response (rho_s < 0) created by the zero-energy Andreev bound
states near an ideal interface (see Fauchere et al. PRL, 82, 3336 (1999),
cond-mat/9901112), into the usual diamagnetic one (rho_s >0).Comment: Extended abstract submitted to "Electron Transport in Mesoscopic
Systems", Satellite conference to LT22, Goteborg, 12-15 August, 1999. 2 pages
Minor changes + the text height problem fixe
Rough Surface Effect on Meissner Diamagnetism in Normal-layer of N-S Proximity-Contact System
Rough surface effect on the Meissner diamagnetic current in the normal layer
of proximity contact N-S bi-layer is investigated in the clean limit. The
diamagnetic current and the screening length are calculated by use of
quasi-classical Green's function. We show that the surface roughness has a
sizable effect, even when a normal layer width is large compared with the
coherence length . The effect is as large as that
of the impurity scattering and also as that of the finite reflection at the N-S
interface.Comment: 12 pages, 3 figures. To be published in J. Phys. Soc. Jpn. Vol.71-
Majorana edge modes of superfluid 3He A-phase in a slab
Motivated by a recent experiment on the superfluid 3He A-phase with a chiral
p-wave pairing confined in a thin slab, we propose designing a concrete
experimental setup for observing the Majorana edge modes that appear around the
circumference edge region. We solve the quasi-classical Eilenberger equation,
which is quantitatively reliable, to evaluate several observables. To derive
the property inherent to the Majorana edge state, the full quantum mechanical
Bogoliubov-de Gennes equation is solved in this setting. On the basis of the
results obtained, we perform decisive experiments to check the Majorana nature.Comment: 5 pages, 5 figure
Quasiparticle States near the Surface and the Domain Wall in a p_x\pm i p_y-Wave Superconductor
The electronic states near a surface or a domain wall in the p-wave
superconductor are studied for the order parameter of the form p_x\pm i
p_y-wave, which is a unitary odd-parity state with broken time-reversal
symmetry. This state has been recently suggested as the superconducting state
of Sr_2 Ru O_4. The spatial variation of the order parameter and vector
potential is determined self-consistently within the quasi-classical
approximation. The local density of states at the surface is constant and does
not show any peak-like or gap-like structure within the superconducting energy
gap, in contrast to the case of the d-wave superconductors. The influence of an
external magnetic field is mainly observable in the energy range above the bulk
gap. On the other hand, there is a small energy gap in the local density of
states at the domain wall between domains of the two degenerate p_x+i p_y-wave
and p_x-i p_y-wave states.Comment: 26 pages, 9 figures, to be published in J. Phys. Soc. Jpn. Vol. 68
(1999) No. 3, erratum: to appear in J. Phys. Soc. Jpn. Vol. 68 (1999) No.
Quasiparticle Bound States and Low-Temperature Peaks of the Conductance of NIS Junctions in d-Wave Superconductors
Quasiparticle states bound to the boundary of anisotropically paired
superconductors, their contributions to the density of states and to the
conductance of NIS junctions are studied both analytically and numerically. For
smooth surfaces and real order parameter we find some general results for the
bound state energies. In particular, we show that under fairly general
conditions quasiparticle states with nonzero energies exist for momentum
directions within a narrow region around the surface normal. The energy
dispersion of the bound states always has an extremum for the direction along
the normal. Along with the zero-bias anomaly due to midgap states, we find, for
quasi two-dimensional materials, additional low-temperature peaks in the
conductance of NIS junctions for voltages determined by the extrema of the
bound state energies. The influence of interface roughness on the conductance
is investigated within the framework of Ovchinnikov's model. We show that
nonzero-bias peaks at low temperatures may give information on the order
parameter in the bulk, even though it is suppressed at the surface.Comment: 14 pages, PostScrip
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