Coexistence of light and heavy surface states in a topological multi-band Kondo insulator

TL;DR

This paper investigates how strong electronic correlations and topology lead to the coexistence of light and heavy surface states in a three-dimensional topological Kondo insulator, with temperature-dependent coherence effects.

Contribution

It reveals the coexistence of light and heavy surface states due to correlations and topology, a novel phenomenon in topological Kondo insulators.

Findings

Heavy surface states form in the surface layer.

Light surface states form in the next-nearest layer.

Heavy states become incoherent at higher temperatures.

Abstract

We analyze the impact of strong correlations on the surface states of a three-dimensional topological Kondo insulator. An important observation is that correlations are strongly increased at the surface, which leads to an energetical confinement of the surface $f$-electrons into a narrow window around the Fermi energy at low enough temperature. This correlation effect in combination with the nontrivial topology has two remarkable consequences: (i) coexistence of light and heavy surface states at low temperatures. While heavy surface states are formed directly in the surface layer, light surface states are formed in the next-nearest surface layer. Furthermore, (ii) with increasing the temperature, the heavy surface states become incoherent and only light surface states can be observed. The coexistence of light and heavy surface states is thereby a remarkable characteristic of the combination of strong correlations and nontrivial topology. We believe that these results are applicable to the candidate topological Kondo insulator SmB6.