Kondo Impurities Coupled to Helical Luttinger Liquid: RKKY-Kondo Physics Revisited

TL;DR

This paper demonstrates that in strongly interacting helical Luttinger Liquids, the Kondo effect dominates over RKKY interactions, a behavior unique to helical systems and not observed in non-helical Luttinger Liquids.

Contribution

It reveals a novel regime where the Kondo effect surpasses RKKY interactions in helical Luttinger Liquids, challenging traditional RKKY-based descriptions.

Findings

Kondo effect dominates over RKKY in strong interactions

Helical nature causes unique Kondo-RKKY crossover

Breakdown of RKKY description in certain regimes

Abstract

We show that the paradigmatic Ruderman-Kittel-Kasuya-Yosida (RKKY) description of two local magnetic moments coupled to propagating electrons breaks down in helical Luttinger Liquids when the electron interaction is stronger than some critical value. In this novel regime, the Kondo effect overwhelms the RKKY interaction over all macroscopic inter-impurity distances. This phenomenon is a direct consequence of the helicity (realized, for instance, at edges of a time-reversal invariant topological insulator) and does not take place in usual (non-helical) Luttinger Liquids.