# Dresden 2006 – wissenschaftliches Programm

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# TT: Tiefe Temperaturen

## TT 4: Correlated Electrons: Quantum Impurities, Kondo Physics

### TT 4.2: Vortrag

### Montag, 27. März 2006, 11:30–11:45, HSZ 301

**Real Time RG for the non-equilibrium Kondo model: Cutoffs set by voltage and decoherence.** — •Thomas Korb^{1}, Herbert Schoeller^{1}, and Jürgen König^{2} — ^{1}Theoretische Physik A, RWTH Aachen, Germany — ^{2}Theoretische Physik III, Ruhr-Universität Bochum

While the equilibrium Kondo effect is well understood there is known less for the Kondo effect in non-equilibrium. The question was raised, if a finite voltage and current induced decoherence prevents the system from going into the strong coupling limit for *V*>*T*_{K} and how to calculate the I-V [1,2].
In [2] a perturbative RG for the scaling of the verticies in non-equilibrium was developed, but the decoherence was included only on the basis of a perturbation calculation.
A different approach was used in [3], where a flow equation analysis was performed on the expense to reside on a Hamiltonian description for the non-equilibrium. There it was found, that the scaling is cutted by balancing of second and third order contributions in the flow equations.
We use the real time RG formalism developed in [4] to analyze the non-equilibrium Kondo effect. It is demonstrated how the cutoffs set by voltage and decoherence rate emerge naturally from a closed set of RG equations on the Keldysh contour (including dephasing of nondiagonal elements of the density matrix). Therefore we are able to calculate the I-V characteristic for *V*>*T*_{K} within one scheme and within a full nonequilibrium formalism.

[1] P. Coleman *et al.*, Phys. Rev. Lett. 86, 4088
(2001).

[2] A. Rosch *et al.*, Phys. Rev. Lett. 90, 076804 (2003).

[3] S. Kehrein, Phys. Rev. Lett. 95, 056602 (2005).

[4] H. Schoeller and J. König, Phys. Rev. Lett. 84, 3686 (2000).