Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 6: Quantum dots and wires: Transport properties I

HL 6.10: Vortrag

Montag, 27. März 2006, 12:30–12:45, BEY 118

Quantum dot system in high magnetic field: From weak to strong tunnel coupling — •Eleonora Storace, Jürgen Weis, and Klaus von Klitzing — Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany

Electrical transport measurements are performed on a quantum dot (QD) system defined as an in-plane structure via etching through a GaAs/AlGaAs heterostructure. Applying a perpendicular magnetic field and increasing afterwards the coupling between the leads and the QD, peaks and valleys of the conductance traces show a smooth transition from the Coulomb blockade oscillations regime to a constant value that is a multiple of e²/h, suggesting the formation of a direct channel between source and drain leads. This behavior is explained considering that, since the geometrical extension of the QD itself is rather large, compressible and incompressible strips are formed along the whole structure and, in the case of strong coupling, the electron wavefunctions in the outer compressible strips in the leads can overlap with the ones in the QD. Tuning the magnetic field through different values of Landau levels filling factor, several electron configurations can be studied; in particular, it is possible to define a situation in which a compressible droplet is present inside the dot region in co-existence with the direct channel, giving rise to an interfering phenomenon known as Fano effect.