559 research outputs found
Andreev reflection in bosonic condensates
We study the bosonic analog of Andreev reflection at a normal-superfluid
interface where the superfluid is a boson condensate. We model the normal
region as a zone where nonlinear effects can be neglected. Against the
background of a decaying condensate, we identify a novel contribution to the
current of reflected atoms. The group velocity of this Andreev reflected
component differs from that of the normally reflected one. For a
three-dimensional planar or two-dimensional linear interface Andreev reflection
is neither specular nor conjugate.Comment: 5 pages, 3 figures. Text revise
Investigation of Peculiarities of the Discharge Excitation with Hollow Cathode Effect in N2 in a Tube Electrode
The influence of some constructive discharge system elements on the electric excitation modes and stable maintaining of pulse glow discharge plasma in N2 in a hollow tube cathode has been investigated. The following discharge system changes have been performed: the position of a hollow electrode-cathode in the dielectric tube-holder; the method of plasma forming gas feeding to the discharge area; the distance between the electrode-cathode and counter-electrode (grounded anode). The investigation has been carried out within 50–700 Pa N2 pressure range. The obtained results may be used in the design of gas discharge systems with hollow cathode effect
Loss of Andreev Backscattering in Superconducting Quantum Point Contacts
We study effects of magnetic field on the energy spectrum in a
superconducting quantum point contact. The supercurrent induced by the magnetic
field leads to intermode transitions between the electron waves that pass and
do not pass through the constriction. The latter experience normal reflections
which couple the states with opposite momenta inside the quantum channel and
create a minigap in the energy spectrum that depends on the magnetic field
Focused Crossed Andreev Reflection
We consider non-local transport in a system with one superconducting and two
normal metal terminals. Electron focusing by weak perpendicular magnetic fields
is shown to tune the ratio between crossed Andreev reflection (CAR) and
electron transfer (ET) in the non-local current response. Additionally,
electron focusing facilitates non-local signals between normal metal contacts
where the separation is as large as the mean free path rather than being
limited by the coherence length of the superconductor. CAR and ET can be
selectively enhanced by modulating the magnetic field
Double Fe-impurity charge state in the topological insulator BiSe
The influence of individual impurities of Fe on the electronic properties of
topological insulator BiSe is studied by Scanning Tunneling Microscopy.
The microscope tip is used in order to remotely charge/discharge Fe impurities.
The charging process is shown to depend on the impurity location in the
crystallographic unit cell, on the presence of other Fe impurities in the close
vicinity, as well as on the overall doping level of the crystal. We present a
qualitative explanation of the observed phenomena in terms of tip-induced local
band bending. Our observations evidence that the specific impurity neighborhood
and the position of the Fermi energy with respect to the Dirac point and bulk
bands have both to be taken into account when considering the electron
scattering on the disorder in topological insulators.Comment: 10 pages, accepted for publication in Applied Physics Letters, minor
bugs were correcte
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