Non-trivial fixed point in a twofold orbitally degenerate Anderson impurity model

TL;DR

This paper investigates a twofold orbitally degenerate Anderson impurity model revealing a robust non-trivial fixed point that could influence the behavior of strongly-correlated lattice systems near a Mott transition.

Contribution

It identifies a more robust non-trivial fixed point in the model, potentially relevant for understanding phases near Mott transitions in lattice systems.

Findings

The fixed point is more stable than the two-impurity Kondo model fixed point.

It can only be destabilized by orbital or gauge symmetry breaking.

The model may explain the emergence of ordered phases near Mott transitions.

Abstract

We study the phase diagram of a twofold orbitally degenerate Anderson impurity model which presents a non-trivial fixed point similar to the two-impurity Kondo model one. Remarkably, this fixed point is more robust than the latter one, since 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 the behavior of a strongly-correlated lattice model close to a Mott transition. We argue that this lattice model should unavoidably encounter the non-trivial fixed point just before the Mott transition and react to its instability by spontaneous generation of an orbital, spin-orbital or superconducting order parameter.