Robust surface states and coherence phenomena in magnetically alloyed SmB6

TL;DR

This study explores the electronic properties of magnetically alloyed SmB6, revealing persistent topological surface states and coherence phenomena despite significant magnetic doping and antiferromagnetism, advancing understanding of topological Kondo insulators.

Contribution

It demonstrates the robustness of topological surface states in SmB6 with high levels of magnetic alloying and links surface state emergence to Kondo gap formation.

Findings

Topologically nontrivial surface and bulk states persist with up to 30% magnetic doping.

Surface states coexist with antiferromagnetism in Eu-doped samples.

Surface state emergence is connected to the formation of a direct Kondo gap.

Abstract

Samarium hexaboride is a candidate for the topological Kondo insulator state, in which Kondo coherence is predicted to give rise to an insulating gap spanned by topological surface states. Here we investigate the surface and bulk electronic properties of magnetically alloyed Sm1-xMxB6 (M=Ce, Eu), using angle-resolved photoemission spectroscopy (ARPES) and complementary characterization techniques. Remarkably, topologically nontrivial bulk and surface band structures are found to persist in highly modified samples with up to 30% Sm substitution, and to coexist with antiferromagnetism in the case of Eu doping. The results are interpreted in terms of a hierarchy of energy scales, in which surface state emergence is linked to the formation of a direct Kondo gap, while low temperature transport trends depend on the indirect gap.