Regensburg 2007 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 11: Quantum dots and wires: Transport properties I

HL 11.8: Vortrag

Montag, 26. März 2007, 16:45–17:00, H15

Nonequilibrium transport through quantum point contacts — •Andreas Helzel, Leonid Litvin, Werner Wegscheider, and Christoph Strunk — Institut für experimentelle und angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany

We investigate the nonequilibrium transport properties through a quantum point contact (QPC) defined by split gates on top of a GaAs/AlGaAs heterostructure with a 230 nm deep 2 DEG. At low temperatures the QPC develops a resonant structure in the differential conductance around zero bias below half of a conductance quantum. Then with increasing conductance this resonance splits in two peaks even in absence of magnetic field. Recent theory [1] suggests for this double peak a double Anderson-impurity arising in the QPC. As already measured before, between 0.7 and 1 conductance quantum a Kondo anomaly can be seen. But in our case with satellites next to it, that merge out of the mentioned split peaks. The Kondo effect can appear in a QPC by a trapped spin in a potential valley arising due to the nonlinear screening of the gate potential in the 2DEG.

[1] T. Rejec, Y. Meir, Nature 442 (2006)