Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.6: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

The Kondo box: a mean-field approach — Rainer Bedrich, •Sebastien Burdin, and Martina Hentschel — Max-Planck-Institut PKS, Nöthnitzer Strasse 38, 01187 Dresden, Germany

We study the Kondo effect induced by a magnetic impurity interacting with a small metallic grain or a quantum dot. Here, in contrast with the Kondo effect occurring in a bulk material, the metallic host is characterised by a finite mean level spacing. This low energy scale can generate deviations from the universal behavior which would be expected for a bulk system. The physical properties of the system are computed within a mean-field approximation for the Kondo interaction. In particular, we study the local magnetic susceptibility, the conductance, and the local density of electronic states as a function of the temperature, the mean level spacing, the Kondo coupling, and the chemical potential. The latter can be experimentally tuned by varying a gate voltage applied to the metallic grain. As a first step, we consider a constant distribution of the non-interacting energy levels. Our results are in agreement with the results obtained from different approaches [1], suggesting that the mean-field approximation is valid. A more realistic situation is then considered, for which the energy levels and wave function amplitudes are distributed following random matrix theory in order to model chaotic mesoscopic systems.

[1] W.B. Thimm, J. Kroha, and J. von Delft, Phys. Rev. Lett. 82, 2143 (1999); R.K. Kaul, G. Zarand, S. Chandrasekharan, D. Ullmo, and H.U. Baranger, Phys. Rev. Lett. 96, 176802 (2006); S. Kettemann, and E.R. Mucciolo, Phys. Rev. B 75, 184407 (2007)