Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 36: TR: Poster Session
TT 36.8: Poster
Donnerstag, 25. März 2010, 14:00–18:00, Poster A
Nonequilibrium cotunneling in quantum dots: Building the bridge between the T-matrix approach and exact perturbation theory — •Georg Begemann1, Sonja Koller1, Milena Grifoni1, and Jens Paaske2 — 1Universität Regensburg — 2Nano-Science Center, University of Copenhagen
Using a T-matrix based rate equation approach, it is possible to perform fast calculations on fourth order transport, i.e. on the cotunneling regime of transport across quantum dots. However, there is the long standing question about the quality of such calculations in comparison to exact, but numerical costly perturbation theory results. In this poster, we present the exact perturbation theory and show the fundamental relation which exists between the two. We can pinpoint to which approximations to the exact method the T-matrix approach corresponds and give a detailed comparison between results on transport across quantum double dots. We also show how an effective Kondo Hamiltonian can be derived in the deep Coulomb blockade regime for Coulomb diamonds with odd filling and that it is equivalent to the fourth order T-matrix contributions.