4,455 research outputs found
Sign Change of the Flux Flow Hall Effect in HTSC
A novel mechanism for the sign change of the Hall effect in the flux flow
region is proposed. The difference between the electron density at
the center of the vortex core and that far outside the vortex causes the
additional contribution to the Hall conductivity . This contribution can be larger than the conventional one in the dirty
case . If the carrier density inside the core exceeds that
far outside, a double sign change may occur as a function of temperature.Comment: 12 pages Latex, no figures, submitted to PR
Proximity Action theory of superconductive nanostructures
We review a novel approach to the superconductive proximity effect in
disordered normal-superconducting (N-S) structures. The method is based on the
multicharge Keldysh action and is suitable for the treatment of interaction and
fluctuation effects. As an application of the formalism, we study the subgap
conductance and noise in two-dimensional N-S systems in the presence of the
electron-electron interaction in the Cooper channel. It is shown that singular
nature of the interaction correction at large scales leads to a nonmonotonuos
temperature, voltage and magnetic field dependence of the Andreev conductance.Comment: RevTeX, 6 pages, 5 eps figures. This is a concise review of
cond-mat/0008463; to be published in the Proceedings of the conference
"Mesoscopic and strongly correlated electron systems" (Chernogolovka, Russia,
July 2000
Peak effect in twinned superconductors
A sharp maximum in the critical current as a function of temperature
just below the melting point of the Abrikosov flux lattice has recently been
observed in both low and high temperature superconductors. This peak effect is
strongest in twinned crystals for fields aligned with the twin planes. We
propose that this peak signals the breakdown of the collective pinning regime
and the crossover to strong pinning of single vortices on the twin boundaries.
This crossover is very sharp and can account for the steep drop of the
differential resistivity observed in experiments.Comment: 4 pages, revtex 3.0, no figure
Transport properties of clean and disordered Josephson junction arrays
We investigate the influence of quantum fluctuations and weak disorder on the
vortex dynamics in a two-dimensional superconducting
Berezinskii-Kosterlitz-Thouless system. The temperature below which quantum
fluctuations dominate the vortex creep is determined, and the transport in this
quantum regime is described. The crossover from quantum to classical regime is
discussed and the quantum correction to the classical current-voltage relation
is determined. It is found that weak disorder can effectively reduce the
critical current as compared to that in the clean system.Comment: 4 pages, 2 figure
Energy losses of fast heavy-ion projectiles in dense hydrogen plasmas
It has been recently shown that the Bethe-Larkin formula for the energy
losses of fast heavy-ion projectiles in dense hydrogen plasmas is corrected by
the electron-ion correlations [Phys. Rev. Lett. \textbf{101}, 075002 (2008)].
We report numerical estimates of this correction based on the values of
obtained by numerical simulations in [Phys. Rev. E \textbf{61},
3470 (2000)]. We also extend this result to the case of projectiles with
dicluster charge distribution. We show that the experimental visibility of the
electron-ion correlation correction is enhanced in the case of dicluster
projectiles with randomly orientated charge centers. Although we consider here
the hydrogen plasmas to make the effect physically more clear, the
generalization to multispecies plasmas is straightforward.Comment: 5 pages, 1 figure. International Conference on Strongly Coupled
Coulomb Systems 2008, Camerino (Italy). To appear in J. Phys.
Bose-Einstein Condensates in Strongly Disordered Traps
A Bose-Einstein condensate in an external potential consisting of a
superposition of a harmonic and a random potential is considered theoretically.
From a semi-quantitative analysis we find the size, shape and excitation
energy as a function of the disorder strength. For positive scattering length
and sufficiently strong disorder the condensate decays into fragments each of
the size of the Larkin length . This state is stable over a large
range of particle numbers. The frequency of the breathing mode scales as
. For negative scattering length a condensate of size
may exist as a metastable state. These finding are generalized to anisotropic
traps
Recovering of superconductivity in exchange fields exceeding Pauli limiting field under spin-dependent quasiparticle distribution
We study theoretically the simultaneous influence of spin accumulation
potential and the Zeeman exchange field on singlet
superconductivity. It is shown that the pair-breaking effect of the Zeeman
field can be fully compensated by creation of the appropriate spin accumulation
potential in the superconductor. Moreover, superconductivity can be recovered
for exchange fields well exceeding the Pauli limiting field. It is proposed
that the effect can be experimentally realized on the basis of voltage biased
junction consisting of a thin superconducting film sandwiched between two half
metals.Comment: 4 pages, 1 figure, published versio
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