15,619 research outputs found
Giant Backscattering Peak in Angle-Resolved Andreev Reflection
It is shown analytically and by numerical simulation that the angular
distribution of Andreev reflection by a disordered normal-metal --
superconductor junction has a narrow peak at the angle of incidence. The peak
is higher than the well-known coherent backscattering peak in the normal state,
by a large factor G/G_0 (where G is the conductance of the junction and
G_0=2e^2/h). The enhanced backscattering can be detected by means of ballistic
point contacts.Comment: Instituut-Lorentz, Leiden, The Netherlands, 4 pages, REVTeX-3.0, 3
figure
Semiclassical theory in Andreev billiards: beyond the diagonal approximation
Recently semiclassical approximations have been successfully applied to study
the effect of a superconducting lead on the density of states and conductance
in ballistic billiards. However, the summation over classical trajectories
involved in such theories was carried out using the intuitive picture of
Andreev reflection rather than the semiclassical reasoning. We propose a method
to calculate the semiclassical sums which allows us to go beyond the diagonal
approximation in these problems. In particular, we address the question of
whether the off-diagonal corrections could explain the gap in the density of
states of a chaotic Andreev billiard.Comment: 11 page
A Study of the Inheritance and the Physiological Behaviour of Dwarfism Associated with an Eye Defect in Rats
Four dwarfed rats recently appeared in two separate closely related litters of an inbred strain of rats in our colony. There was associated with the dwarfed condition a marked opacity of the eyes apparently causing blindness
Suppression of Giant Magnetoresistance by a superconducting contact
We predict that current perpendicular to the plane (CPP) giant
magnetoresistance (GMR) in a phase-coherent magnetic multilayer is suppressed
when one of the contacts is superconducting. This is a consequence of a
superconductivity-induced magneto-resistive (SMR) effect, whereby the
conductance of the ferromagnetically aligned state is drastically reduced by
superconductivity. To demonstrate this effect, we compute the GMR ratio of
clean (Cu/Co)_nCu and (Cu/Co)_nPb multilayers, described by an ab-initio spd
tight binding Hamiltonian. By analyzing a simpler model with two orbitals per
site, we also show that the suppression survives in the presence of elastic
scattering by impurities.Comment: 5 pages, 4 figures. Submitted to PR
Quantum-limited mass flow of liquid He
We consider theoretically the possibility of observing unusual quantum fluid
behavior in liquid He and solutions of He in He systems
confined to nano-channels. In the case of pure ballistic flow at very low
temperature conductance will be quantized in units of . We show that
these steps should be sensitive to increases in temperature. We also use of a
random scattering matrix simulation to study flow with diffusive wall
scattering. Universal conductance fluctuations analogous to those seen in
electron systems should then be observable. Finally we consider the possibility
of the cross-over to a one-dimensional system at sufficiently low temperature
where the system could form a Luttinger liquid
Superconducting Proximity Effect and Universal Conductance Fluctuations
We examine universal conductance fluctuations (UCFs) in mesoscopic
normal-superconducting-normal (N-S-N) structures using a numerical solution of
the Bogoliubov - de Gennes equation. We discuss two cases depending on the
presence (``open'' structure) or absence (``closed'' structure) of
quasiparticle transmission. In contrast to N-S structures, where the onset of
superconductivity increases fluctuations, we find that UCFs are suppressed by
superconductivity for N-S-N structures. We demonstrate that the fluctuations in
``open'' and ``closed'' structures exhibit distinct responses to an applied
magnetic field and to an imposed phase variation of the superconducting order
parameter.Comment: (4 pages, 5 figures). Corrected typos in equations, added references,
changed Fig. 5 and its discussions. Phys. Rev. B, accepted for publicatio
Phase coherent transport in hybrid superconducting structures: the case of d-wave superconductors
We examine the effect of d-wave symmetry on zero bias anomalies in
normal-superconducting tunnel junctions and phase-periodic conductances in
Andreev interferometers. In the presence of d-wave pairing, zero-bias anomalies
are suppressed compared with the s-wave case. For Andreev interferometers with
aligned islands, the phase-periodic conductance is insensistive to the nature
of the pairing, whereas for non-aligned islands, the nature of the zero-phase
extremum is reversed.Comment: 10 Pages, Revtex. 11 postscript figures available on reques
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