100 research outputs found
Scattering problems and boundary conditions for 2D electron gas and graphene
Structure and coordinate dependence of the reflected wave, as well as
boundary conditions for quasi-particles of graphene and the two dimensional
electron gas in sheets with abrupt lattice edges are obtained and analyzed by
the Green's function technique. In particular, the reflection wave function
contains terms inversely proportional to the distance to the graphene lattice
edge. The Dirac equation and the momentum dependence of the wave functions of
the quasi-particles near the conical points are also found by the perturbation
theory with degeneracy in terms of the Bloch functions taken at the degeneracy
points. The developed approach allows to formulated the validity criteria for
the Dirac equation in a rather simple way.Comment: 7 pages, 2 figure
Giant oscillations of the current in a dirty 2D electron system flowing perpendicular to a lateral barrier under magnetic field
The charge transport in a dirty 2-dimensional electron system biased in the
presence of a lateral potential barrier under magnetic field is theoretically
studied. The quantum tunneling across the barrier provides the quantum
interference of the edge states localized on its both sides that results in
giant oscillations of the charge current flowing perpendicular to the lateral
junction. Our theoretical analysis is in a good agreement with the experimental
observations presented in Ref.8. In particular, positions of the conductance
maxima coincide with the Landau levels while the conductance itself is
essentially suppressed even at the energies at which the resonant tunneling
occurs and hence these puzzling observations can be resolved without taking
into account the electron-electron interaction.Comment: 6 pages, 4 figure
Enhancement of magnetic ordering by the stress fields of grain boundaries in ferromagnets
In the paper we predict a distinctive change of magnetic properties and
considerable increase of the Curie temperature caused by the strain fields of
grain boundaries in ferromagnetic films. It is shown that a sheet of
spontaneous magnetization may arise along a grain boundary at temperatures
greater than the bulk Curie temperature. The temperature dependence and space
distribution of magnetization in a ferromagnetic film with grain boundaries are
calculated. We found that grain boundaries can produce long-range
strain fields that results in the width of the magnetic sheet along the
boundary of the order of at temperatures grater than the
bulk Curie temperature by about K.Comment: 5 pages, 3 Figures include
Giant conductance oscillations in a normal mesoscopic ring induced by an SNS Josephson current
A theoretical explanation of giant conductance oscillations observed in
normal mesoscopic rings with superconducting ``mirrors" is proposed. The effect
is due to resonant tuning of Andreev levels to the Fermi level, which enhances
the transparency of the system to the normal current. The mechanism is
demonstrated for a one-dimensional model system.Comment: 10 pages, RevTeX, 3 fig. available upon request, Appl. Phys. Report
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Magnetotransport in the presence of a longitudinal barrier: multiple quantum interference of edge states
Transport in a two-dimensional electron gas subject to an external magnetic
field is analyzed in the presence of a \textit{longitudinal barrier.} We show
that \textit{quantum interference of the edge states} bound by the longitudinal
barrier results in a drastic change of the electron motion: the degenerate
discrete Landau levels are transformed into an alternating sequence of energy
bands and energy gaps. These features of the electron spectrum should result in
a high sensitivity of thermodynamic and transport properties of the 2D electron
gas to external fields. In particular, we predict giant oscillations of the
ballistic conductance and discuss nonlinear current-voltage characteristics,
coherent Bloch oscillations and effects of impuritiesComment: 4 pages, 3 figure
Influence of the Rashba effect on the Josephson current through a superconductor/Luttinger liquid/superconductor tunnel junction
The Josephson current through a 1D quantum wire with Rashba spin-orbit and
electron-electron interactions is calculated. We show that the interplay of
Rashba and Zeeman interactions gives rise to a supercurrent through the 1D
conductor that is anomalous in the sense that it persists in the absence of any
phase difference between the two superconducting leads to which it is attached.
The electron dispersion asymmetry induced by the Rashba interaction in a
Luttinger-liquid wire plays a significant role for poorly transmitting
junctions. It is shown that for a weak or moderate electron-electron
interaction the spectrum of plasmonic modes confined to the normal part of the
junction becomes quasi-random in the presence of dispersion asymmetry.Comment: 25 pages, 3 figure
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