29 research outputs found
Multitip scanning gate microscopy for ballistic transport studies in systems with two-dimensional electron gas
We consider conductance mapping of systems based on the two-dimensional
electron gas with scanning gate microscopy using two and more tips of the
atomic force microscope. The paper contains results of numerical simulations
for a model tip potential with a proposal of a few procedures for extraction
and manipulation the ballistic transport properties. In particular, we
demonstrate that the multi-tip techniques can be used for readout of the Fermi
wavelength, detection of potential defects, filtering specific transverse
modes, tuning the system into resonant conditions under which a stable map of a
local density of states can be extracted from conductance maps using a third
tip.Comment: 9 pages, 12 figure
Conductance measurement of spin-orbit coupling in the two-dimensional electron systems with in-plane magnetic field
We consider determination of spin-orbit (SO) coupling constants for the
two-dimensional electron gas from measurements of electric properties in
rotated in-plane magnetic field. %Due to the interplay Due to the SO coupling
the electron backscattering is accompanied by spin precession and spin mixing
of the incident and reflected electron waves. The competition of the external
and SO-related magnetic fields produces a characteristic conductance dependence
on the in-plane magnetic field value and orientation which, in turn, allows for
determination of the absolute value of the effective spin-orbit coupling
constant as well as the ratio of the Rashba and Dresselhaus SO contributions.Comment: 4 pages + supplementary material
Interference features in scanning gate conductance maps of quantum point contacts with disorder
We consider quantum point contacts (QPCs) defined within disordered
two-dimensional electron gases as studied by scanning gate microscopy. We
evaluate the conductance maps in the Landauer approach and wave function
picture of electron transport for samples with both low and high electron
mobility at finite temperatures. We discuss the spatial distribution of the
impurities in the context of the branched electron flow. We reproduce the
surprising temperature stability of the experimental interference fringes far
from the QPC. Next, we discuss -- previously undescribed -- funnel-shaped
features that accompany splitting of the branches visible in previous
experiments. Finally, we study elliptical interference fringes formed by an
interplay of scattering by the point-like impurities and by the scanning probe.
We discuss the details of the elliptical features as functions of the tip
voltage and the temperature, showing that the first interference fringe is very
robust against the thermal widening of the Fermi level. We present a simple
analytical model that allows for extraction of the impurity positions and the
electron gas depletion radius induced by the negatively charged tip of the
atomic force microscope, and apply this model on experimental scanning gate
images showing such elliptical fringes