Kondo-induced hybrid topological insulator in two-dimensional electron system with a quadratic band crossing point

TL;DR

This paper explores how the Kondo effect in a 2D electron system with quadratic band crossing induces a novel hybrid topological insulator phase combining quantum anomalous Hall and quantum spin Hall effects, featuring edge currents.

Contribution

It demonstrates that the Kondo effect can create a new hybrid topological phase with coexisting quantum anomalous Hall and spin Hall effects in a 2D system with quadratic band crossing.

Findings

Induction of a hybrid topological insulator phase by the Kondo effect.

Presence of quantized charge and spin currents at edges.

Coexistence of quantum anomalous Hall and quantum spin Hall effects.

Abstract

We investigate the Kondo effect in the two-dimensional electron system with a non-trivial quadratic energy band crossing point. We show that the Kondo effect can induce a new hybrid topological insulator phase which is a coexistence state of the quantum anomalous Hall effect and the TRSbroken quantum spin Hall effect. This hybrid topological insulator exhibits not only a quantized charge Hall current but also a net spin current, which are localized at the edge boundaries. This peculiar topological state arises due to the interplay of two marginally relevant operators, i.e., the Kondo-coupling between the electrons and the local magnetic moment and the electron-electron interaction in the two-dimensional system.