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TT: Fachverband Tiefe Temperaturen

TT 38: Poster Session Transport

TT 38.9: Poster

Mittwoch, 16. März 2011, 14:00–18:00, P3

Kondo effect in quantum dots: slave-boson Keldysh field theory — •Sergey Smirnov and Milena Grifoni — Institut für Theoretische Physik, Universität Regensburg

We consider a single impurity Anderson model, a quantum dot with a single spin degenerate level coupled to two contacts possibly at different chemical potentials. Assuming strong electron-electron interactions in the dot we restrict the dot Hilbert space to a subspace of the empty and singly occupied states at the expense of transforming to new fermions and introducing a slave-boson. Using this new fermi-bose representation we construct an effective Keldysh field theory suitable for both equilibrium and non-equilibrium situations. The conservation of the total number of the fermions and bosons leads to a constraint in the integration over the fermionic and bosonic fields. This mathematical complication, a consequence of the interacting nature of the problem, is dealt with by introducing an additional integration removing the constraint. After integrating over the fermionic fields of the dot and contacts we obtain an effective Keldysh action with respect to the dot slave-bosonic field. We further develop a saddle point analysis of this action equivalent to the mean field approach known from the imaginary time equilibrium field theories developed previously for the Kondo effect.