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Regensburg 2000 – scientific programme

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HL: Halbleiterphysik

HL 32: Quantenpunkte

HL 32.4: Talk

Thursday, March 30, 2000, 11:15–11:30, H15

Resonant Tunneling through Multi-level Quantum Dots — •Daniel Boese1, Teemu Pohjola1,2, Herbert Schoeller3,1, and Gerd Schön11Institut für Theoretische Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe — 2Materials Physics Laboratory, Helsinki University of Technology, P.O. Box 2200, 02015 - HUT, Finland — 3Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021 Karlsruhe

Recent progress in nanofabrication technology lead to the observation of the Kondo effect in semiconductor quantum dots.[1] Moreover it now becomes feasible to tune most system parameters. Therefore we study the transport properties of multi-level quantum dots. In particular we investigate the non-linear conductance of a quantum dot with a non-conserved level index, which shows signatures of an orbital Kondo model.
We approach the problem by calculating the time evolution of the density matrix by a real time diagrammatic technique. The Keldysh formalism allows us to calculate quantities for finite bias voltage, i.e. out of equilibrium. Utilizing the resonant tunneling approximation we find that the spectral density develops strong peaks at the Fermi edges of the reservoirs. We also calculate the conductance via a poor man’s scaling approach.

[1] D. Goldhaber-Gordon et al., Nature(London) 391, 156 (1998), S.M. Cronenwett et al., Science 281, 540 (1998)

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