Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 30: Quantum dots and wires: Transport properties II
HL 30.5: Vortrag
Dienstag, 26. Februar 2008, 15:15–15:30, ER 164
Back-action of a biased quantum point contact on an unbiased double quantum dot — •Daniela Taubert1, Daniel Harbusch1, Hans-Peter Tranitz2, Werner Wegscheider2, and Stefan Ludwig1 — 1Center for NanoScience and Department für Physik, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München — 2Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg
We experimentally study the back-action of a quantum point contact (QPC) on a widely tunable double quantum dot (DQD) in the few electron regime. This nanostructure is electrostatically defined in the two-dimensional electron gas of a high mobility AlGaAs/GaAs heterostructure. The stability diagram of the unbiased DQD is measured using the QPC as charge detector. For this biasing the QPC is necessary, thus causing it to act additionally as a non-equilibrium energy source.
The influence of this source of energy can be seen in the stability diagram: In the regime of small tunnel coupling between one of the dots and the leads we observe disappearing charging linees. Increasing the QPC bias voltage causes reappearance and an additional shift of these charging lines which points to a non-equilibrium situation with modified tunneling rates.
Within a simple model we consider absorption of energy quanta originating from the non-equilibrium energy source by the DQD. The modification of tunneling rates caused by this energy transfer explains our findings.