8 research outputs found
Probing a Kondo correlated quantum dot with spin spectroscopy
We investigate Kondo effect and spin blockade observed on a many-electron
quantum dot and study the magnetic field dependence. At lower fields a
pronounced Kondo effect is found which is replaced by spin blockade at higher
fields. In an intermediate regime both effects are visible. We make use of this
combined effect to gain information about the internal spin configuration of
our quantum dot. We find that the data cannot be explained assuming regular
filling of electronic orbitals. Instead spin polarized filling seems to be
probable.Comment: 4 pages, 5 figure
A Schottky top-gated two-dimensional electron system in a nuclear spin free Si/SiGe heterostructure
We report on the realization and top-gating of a two-dimensional electron
system in a nuclear spin free environment using 28Si and 70Ge source material
in molecular beam epitaxy. Electron spin decoherence is expected to be
minimized in nuclear spin-free materials, making them promising hosts for
solid-state based quantum information processing devices. The two-dimensional
electron system exhibits a mobility of 18000 cm2/Vs at a sheet carrier density
of 4.6E11 cm-2 at low temperatures. Feasibility of reliable gating is
demonstrated by transport through split-gate structures realized with palladium
Schottky top-gates which effectively control the two-dimensional electron
system underneath. Our work forms the basis for the realization of an
electrostatically defined quantum dot in a nuclear spin free environment.Comment: 8 pages, 3 figure
Asymmetric nonlinear response of the quantized Hall effect
An asymmetric breakdown of the integer quantized Hall effect (IQHE) is investigated. This rectification effect is observed as a function of the current value and its direction in conjunction with an asymmetric lateral confinement potential defining the Hall bar. Our electrostatic definition of the Hall bar via Schottky gates allows a systematic control of the steepness of the confinement potential at the edges of the Hall bar. A softer edge (flatter confinement potential) results in more stable Hall plateaus, i.e. a breakdown at a larger current density. For one soft and one hard edge, the breakdown current depends on its direction, resembling rectification. This nonlinear magneto-transport effect confirms the predictions of an emerging screening theory of the IQHE.ISSN:1367-263
Asymmetric nonlinear response of the quantized Hall effect
An asymmetric breakdown of the integer quantized Hall effect (IQHE) is investigated. This rectification effect is observed as a function of the current value and its direction in conjunction with an asymmetric lateral confinement potential defining the Hall bar. Our electrostatic definition of the Hall bar via Schottky gates allows a systematic control of the steepness of the confinement potential at the edges of the Hall bar. A softer edge (flatter confinement potential) results in more stable Hall plateaus, i.e. a breakdown at a larger current density. For one soft and one hard edge, the breakdown current depends on its direction, resembling rectification. This nonlinear magnetotransport effect confirms the predictions of an emerging screening theory of the IQHE
Asymmetric nonlinear response of the quantized Hall effect
An asymmetric break-down of the integer quantized Hall effect is
investigated. This rectification effect is observed as a function of the
current value and its direction in conjunction with an asymmetric lateral
confinement potential defining the Hall-bar. Our electrostatic definition of
the Hall-bar via Schottky-gates allows a systematic control of the steepness of
the confinement potential at the edges of the Hall-bar. A softer edge (flatter
confinement potential) results in more stable Hall-plateaus, i.e. a break-down
at a larger current density. For one soft and one hard edge the break-down
current depends on the current direction, resembling rectification. This
non-linear magneto-transport effect confirms the predictions of an emerging
screening theory of the IQHE.Comment: 4 Pages, 4 Figure