54 research outputs found
Metal-Insulator oscillations in a Two-dimensional Electron-Hole system
The electrical transport properties of a bipolar InAs/GaSb system have been
studied in magnetic field. The resistivity oscillates between insulating and
metallic behaviour while the quantum Hall effect shows a digital character
oscillating from 0 to 1 conducatance quantum e^2/h. The insulating behaviour is
attributed to the formation of a total energy gap in the system. A novel looped
edge state picture is proposed associated with the appearance of a voltage
between Hall probes which is symmetric on magnetic field reversal.Comment: 4 pages, 5 Postscript figures: revised versio
Tunneling transverse to a magnetic field, and how it occurs in correlated 2D electron systems
We investigate tunneling decay in a magnetic field. Because of broken
time-reversal symmetry, the standard WKB technique does not apply. The decay
rate and the outcoming wave packet are found from the analysis of the set of
the particle Hamiltonian trajectories and its singularities in complex space.
The results are applied to tunneling from a strongly correlated 2D electron
system in a magnetic field parallel to the layer. We show in a simple model
that electron correlations exponentially strongly affect the tunneling rate.Comment: 4 pages, 3 figure
Tunneling decay in a magnetic field
We provide a semiclassical theory of tunneling decay in a magnetic field and
a three-dimensional potential of a general form. Because of broken
time-reversal symmetry, the standard WKB technique has to be modified. The
decay rate is found from the analysis of the set of the particle Hamiltonian
trajectories in complex phase space and time. In a magnetic field, the
tunneling particle comes out from the barrier with a finite velocity and behind
the boundary of the classically allowed region. The exit location is obtained
by matching the decaying and outgoing WKB waves at a caustic in complex
configuration space. Different branches of the WKB wave function match on the
switching surface in real space, where the slope of the wave function sharply
changes. The theory is not limited to tunneling from potential wells which are
parabolic near the minimum. For parabolic wells, we provide a bounce-type
formulation in a magnetic field. The theory is applied to specific models which
are relevant to tunneling from correlated two-dimensional electron systems in a
magnetic field parallel to the electron layer.Comment: 16 pages, 11 figure
Giant negative magnetoresistance in semiconductors doped by multiply charged deep impurities
A giant negative magnetoresistance has been observed in bulk germanium doped
with multiply charged deep impurities. Applying a magnetic field the resistance
may decrease exponentially at any orientation of the field. A drop of the
resistance as much as about 10000% has been measured at 6 T. The effect is
attributed to the spin splitting of impurity ground state with a very large
g-factor in the order of several tens depending on impurity.Comment: 4 pages, 4 figure
Shubnikov-De Haas study in laterally constricted GaAs-AlGaAs heterojunctions$
SIGLEAvailable from British Library Document Supply Centre- DSC:DX84858 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Interface composition dependence of the band offset in InAs/GaSb
We have performed 4 K magnetotransport measurements on intrinsic InAs/GaSb multi quantum wells (MQWs) under hydrostatic pressure. Through careful configuration of the growth we are able to produce samples that have differing interface monolayers (either InSb or GaAs). Analysing the data to calculate the band overlap (Delta), we find that InSb-like samples have an overlap 30 meV larger than GaAs-like in good agreement with recent theoretical predictions
Optical probing of the minigap in InAs/GaSb superlattices
We report large modulations in the far infrared absorption of semimetallic InAs/GaSb superlattices in parallel field. The strong absorption is attributed to direct transitions across the minigap at the point where the electron and hole dispersions anticross. The measured minigap energy is found to be in the range 3-10 meV depending on the structure of the sample. The optical results are compared to parallel field magnetoresistance measurements and also to theory using an 8 band k . p calculation. (C) 1998 Elsevier Science B.V. All rights reserved
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