Interaction-driven transition between topological states in a Kondo insulator

TL;DR

This paper investigates how electron interactions in Kondo insulators with spin-orbit coupling can induce a transition between different topological states, revealing a new interaction-driven topological phase with edge modes.

Contribution

It demonstrates an interaction-driven topological phase transition in a Kondo insulator model using DMFT, linking electron correlations to topological state changes.

Findings

Interaction-driven transition between topological states

Observation of a bulk gap closing and Z2 invariant change

Existence of a topological heavy fermion phase with edge modes

Abstract

Heavy fermion materials naturally combine strong spin-orbit interactions and electronic correlations. When there is precisely one conduction electron per impurity spin, the coherent heavy fermion state is insulating. This Kondo insulating state has recently been argued to belong to the class of quantum spin Hall states. Motivated by this conjecture and a very recent experimental realization of this state, we investigate a model for Kondo insulators with spin-orbit coupling. Using DMFT, we observe an interaction-driven transition between two distinct topological states, indicated by a closing of the bulk gap and a simultaneous change of the Z2 topological invariant. At large interaction strength we find a topological heavy fermion state, characterized by strongly renormalized heavy bulk bands, hosting a pair of zero-energy edge modes. The model allows a detailed understanding of the temperature dependence of the single particle spectral function and in particular the energy scales at which one observes the appearance of edge states within the bulk gap.