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HL: Halbleiterphysik
HL 39: Quantenpunkte und -dr
ähte: Transporteigenschaften I
HL 39.2: Vortrag
Montag, 7. März 2005, 10:15–10:30, TU P-N202
Kondo effect versus spin blockade — •D. Kupidura1, M. C. Rogge1, R. J. Haug1, and W. Wegscheider2 — 1Institut für Festkörperphysik, Universität Hannover, D-30167 Hannover — 2Angewandte und Experimentelle Physik, Universität Regensburg, D-93040 Regensburg
We report a competition between Kondo effect and spin blockade in a lateral quantum dot defined by local anodic oxidation on a GaAs/AlGaAs-heterostructure. We observe magnetically induced chessboard patterns in the conductance of our system what suggests Kondo correlations between electronic spins in the leads and an unpaired spin within the quantum dot. Thus the dot forms a spin singlet with the leads. Additionally we observe a spin blockade phenomenon, which is correlated with a spin polarization of the 2-dimensional leads in a magnetic field. This polarization destroys the spin up/spin down superposition of the Kondo singlet. Thus along with the onset of this spin blockade we find a suppression of the Kondo effect.