Nontrivial fixed point in a twofold orbitally degenerate Anderson impurity model

Abstract

We study a twofold orbitally degenerate Anderson impurity model which shows a nontrivial fixed point similar to that of the two-impurity Kondo model, but remarkably more robust, as it can only be destabilized by orbital- or gauge-symmetry breaking. The impurity model is interesting per se, but here our interest is rather in the possibility that it might be representative of a strongly correlated lattice model close to a Mott transition. We argue that this lattice model should unavoidably encounter the nontrivial fixed point just before the Mott transition and react to its instability by spontaneous generation of an orbital, spin-orbital or superconducting order parameter.