Fragility of the Kondo insulating gap against disorder: Relevance to recent puzzles in topological Kondo insulators

Abstract

Kondo insulators are strongly correlated systems in which a clean insulating gap emerges only at very low temperature due to many-body effects involving localized f electrons. However, certain Kondo insulators, like SmB_{6} and Ce_{3}Bi_{4}Pt_{3}, display metallic behaviors at extremely low temperature and have defied current understanding. Recent advances in topological effects in materials have raised attention on the protected surface states in these “topological Kondo insulators” as a potential resolution to some of the puzzling behaviors. Here we resolve these puzzles via a different route, by showing that the emergent Kondo insulating scale is extremely vulnerable against a moderate degree of disorder, such that the gap is filled with a small number of states. Therefore, the real samples are probably never truly insulating and this in turn compromises the essential building block of topological considerations. Our results suggest strongly that systems like the Slater insulators would be a more promising direction to extend the realm of topology to strongly correlated systems.