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HL: Halbleiterphysik
HL 39: Quantenpunkte und -dr
ähte: Transporteigenschaften I
HL 39.5: Talk
Monday, March 7, 2005, 11:00–11:15, TU P-N202
Investigation of spin blockade in a quantum dot using a quantum point contact as a charge detector — •C. Fricke1, M. C. Rogge1, B. Harke1, F. Hohls1, R. J. Haug1, and W. Wegscheider2 — 1Institut für Festkörperphysik, Universität Hannover, D-30167 Hannover — 2Angewandte und Experimentelle Physik, Universität Regensburg, D-93040 Regensburg
We show transport measurements in high magnetic field on a coupled system including a quantum dot and a quantum point contact. We use a GaAs/AlGaAs heterostructure containing a two-dimensional electron system (2DES) 34 nm below the surface. The lateral quantum dot and the quantum point contact (QPC) are defined by an atomic force microscope (AFM) using the local anodic oxidation (LAO). We perform our measurements in a 3He/4He dilution refrigerator with a superconductive magnet. Transport through the quantum dot and the quantum point contact are measured at the same time. We thereby use the QPC as a charge detector. Thus we can observe charge fluctuations on the dot with high sensitivity, even when the current through the dot is too low for transport measurements. At high magnetic field we observe spin blockade on the dot. In this regime charge redistributions due to the magnetic field lead to a change in the effective charge detected by the QPC.