242 research outputs found
Coulomb-enhanced resonance transmission of quantum SINIS junctions
Coherent charge transfer through a ballistic gated SINIS junction is mediated
by the resonant tunneling via the Andreev states. Extra charge accommodated on
the Andreev levels partially compensates the charge induced by the gate voltage
preserving the electron wavelength and maintaining the resonance conditions in
a broad range of gate voltages. As a result, the transparency of the junction
as well as the supercurrent trough it can be substantially increased as
compared to the zero-Coulomb case
Coulomb Promotion of Spin-Dependent Tunnelling
We study transport of spin-polarized electrons through a magnetic
single-electron transistor (SET) in the presence of an external magnetic field.
Assuming the SET to have a nanometer size central island with a single electron
level we find that the interplay on the island between coherent spin-flip
dynamics and Coulomb interactions can make the Coulomb correlations promote
rather than suppress the current through the device. We find the criteria for
this new phenomenon -- Coulomb promotion of spin-dependent tunnelling -- to
occur.Comment: 4 pages, 3 figures; The new version has a slightly modified title, 2
more figures, and an extended analysis of the (same) results obtaine
Orbital ac spin-Hall effect in the hopping regime
The Rashba and Dresselhaus spin-orbit interactions are both shown to yield
the low temperature spin-Hall effect for strongly localized electrons coupled
to phonons. A frequency-dependent electric field generates a
spin-polarization current, normal to , due to interference of hopping
paths. At zero temperature the corresponding spin-Hall conductivity is real and
is proportional to . At non-zero temperatures the coupling to the
phonons yields an imaginary term proportional to . The interference
also yields persistent spin currents at thermal equilibrium, at .
The contributions from the Dresselhaus and Rashba interactions to the
interference oppose each other.Comment: 4 pages, no figure
Memory effects in transport through a hopping insulator: Understanding two-dip experiments
We discuss memory effects in the conductance of hopping insulators due to
slow rearrangements of many-electron clusters leading to formation of polarons
close to the electron hopping sites. An abrupt change in the gate voltage and
corresponding shift of the chemical potential change populations of the hopping
sites, which then slowly relax due to rearrangements of the clusters. As a
result, the density of hopping states becomes time dependent on a scale
relevant to rearrangement of the structural defects leading to the excess time
dependent conductivity
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