Non-Kondo-like Electronic Structure in the Correlated Rare-Earth Hexaboride

Abstract

We present angle-resolved photoemission studies on the rare-earth hexaboride YbB6, which has recently been predicted to be a topological Kondo insulator. Our data do not agree with the prediction and instead show that YbB6 exhibits a novel topological insulator state in the absence of a Kondo mechanism. We find that the Fermi level electronic structure of YbB6 has three 2D Dirac cone like surface states enclosing the Kramers’ points, while the f-orbital which would be relevant for the Kondo mechanism is ∼ 1 eV below the Fermi level. Our first-principles calculation shows that the topological state which we observe in YbB6 is due to an inversion between Yb d and B p bands. These experimental and theoretical results provide a new approach for realizing novel correlated topological insulator states in rare-earth materials.