Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 30: Correlated Electrons: Quantum Impurities, Kondo Physics
TT 30.9: Talk
Tuesday, March 12, 2013, 11:45–12:00, H21
Out-of-equilibrium steady-states near quantum critical points - A dynamical large-N study of the Bose-Fermi Kondo model — •Pedro Ribeiro1 and Stefan Kirchner1,2 — 1Max Planck Institute for the Physics of Complex Systems - Nothnitzer Str. 38, , D-01187 Dresden, Germany — 2Max Planck Institute for Chemical Physics of Solids - Nothnitzer Str. 40, D-01187 Dresden, Germany
We study the out-of-equilibrium steady state properties of the Bose-Fermi-Kondo model, describing a local magnetic moment coupled to two ferromagnetic leads that support bosonic (magnons) and fermionic (Stoner continuum electrons) low energy excitations. In equilibrium, this model describes the destruction of the Kondo effect as the coupling to the bosons is increased, its phase diagram comprises three non-trivial fixed points. Using a dynamical large-N approach on the Keldysh contour, we study two different non-equilibrium setups: (a) a finite bias voltage and (b) a finite temperature gradient, imposed across the leads. The scaling behavior of the charge and energy currents is identified and characterized for the different fixed points. We report the existence of an effective temperature, defined based on the fluctuation dissipation relations of the local spin-susceptibility, that permits to recover the equilibrium scaling behavior of both dynamical and static spin susceptibilities in all the studied cases.