Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: Transport: Nanoelectronics I - Quantum Dots, Wires, Point Contacts 3

TT 21.13: Talk

Tuesday, March 27, 2012, 12:45–13:00, BH 334

Keldysh field integral theory for the Kondo effect in interacting nanoscopic systems — •Sergey Smirnov and Milena Grifoni — Institut für Theoretische Physik, Universität Regensburg

We derive a nonequilibrium Keldysh field theory valid for a system with finite electron-electron interactions much stronger than the coupling of the system to contacts. Finite electron-electron interactions are treated involving as many slave-boson degrees of freedom as one needs for a concrete many-body system. For clarity the theory is presented for the Kondo regime of the single impurity Anderson model. The effective Keldysh action takes into account weak slave-bosonic oscillations excited by the electronic tunneling between the nanoscopic system and contacts. This allows us to derive an analytical expression for the tunneling density of states at temperatures close to and above the Kondo temperature [1,2]. The differential conductance is then obtained as a function of an external voltage. We also obtain the temperature dependence of the linear conductance and compare it with the one obtained in numerical renormalization group calculations. We find that our Keldysh field integral theory predicts a universal temperature dependence of the linear conductance and that the scaling of this dependence is given by the standard Kondo temperature.
S. Smirnov and M. Grifoni, Phys. Rev. B 84, 125303 (2011).
S. Smirnov and M. Grifoni, arXiv:1109.1540.