Non-Kondo-like Electronic Structure in the Correlated Rare-Earth   Hexaboride YbB$_6$
  We present angle-resolved photoemission studies on the rare-earth hexaboride YbB$_6$, which has recently been predicted to be a topological Kondo insulator. Our data do not agree with the prediction and instead show that YbB$_6$ exhibits a novel topological insulator state in the absence of a Kondo mechanism. We find that the Fermi level electronic structure of YbB$_6$ 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 $\sim1$ eV below the Fermi level. Our first-principles calculation shows that the topological state which we observe in YbB$_6$ 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. 
Madhab Neupane, Su-Yang Xu, Nasser Alidoust, Guang Bian, Dae-Jeong   Kim, Chang Liu, Ilya Belopolski, Tay-Rong Chang, Horng-...
cond-mat.str-el