Mean-field results on the Anderson impurity model out of equilibrium

We investigate the mean-field phase diagram of the Anderson impurity model out of equilibrium. Generalizing the unrestricted Hartree-Fock approach to the nonequilibrium situation we derive and analyze the system of equations defining the critical surface separating the magnetic regime from the nonmagnetic one. An exact analytic solution for the phase boundary as a function of the applied voltage is found in the symmetric case. Surprisingly, we find that as soon as there is an asymmetry, even small, between the contacts, no finite voltage is able to destroy the magnetic regime which persists at arbitrary high voltages.