Exact results on the out-of-equilibrium Kondo model
Edouard Boulat, Université Paris Diderot
Transport in nanoscale quantum devices can be described in many situations by quantum impurity models in which the low energy regime is a strong coupling (SC) regime, an archetypical example being the Kondo model. Equilibrium properties in this regime are non perturbative but nevertheless fully accessible using integrability.
After discussing why the exact solution *at equilibrium* cannot be in general extended to describe the out-of-equilibrium situations, I will describe a recently developed framework for integrable quantum impurity models , in which we can exactly tackle various out-of-equilibrium situations in their SC regime, using their equilibrium integrability properties. It allows to compute directly the expansion of the universal scaling functions for physical quantities (like the electrical current), in principle to arbitrarily high order in the driving out-of-equilibrium, be it voltage, frequency… In particular, we show how to apply this to the Kondo model : our approach successfully goes beyond known results for the electrical current and noise.
 L.Freton and E.Boulat, PRL 112, 216802 (2014).