摘要
The rare-earth hexaboride SmB 6 , known as the topological Kondo insulator, has attracted tremendous attention in recent years. It was revealed that the topological phase of SmB 6 is insensitive to the value of on-site Coulomb interactions (Hubbard U), indicating that the topological phase in SmB 6 is robust against strong correlations. On the contrary, the isostructural YbB 6 displays a sensitivity to the Hubbard U value. As U increases, YbB 6 transforms from topological Kondo insulator to trivial insulator, showing the weak robustness of the topological phase of YbB 6 against U. Consequently, the dependence of the topological phase on Hubbard U is a crucial issue in the rare-earth hexaboride family. In this work, we investigate the structural and electronic properties of rare-earth hexaboride compounds through first-principles calculations based on density functional theory. By taking the strong correlations into consideration using a wide range of on-site U values, we study the evolution of the topological phases in rare-earth hexaboride (XB 6 , X = La, Ce, Pr, Nd, Pm, Sm, Eu). Unlike YbB 6 , the topological trends in all the examples of XB 6 studied in this work are insensitive to the U values. We conclude that in addition to the well-known SmB 6 , PmB 6 , NdB 6 and EuB 6 are also topologically nontrivial compounds, whereas LaB 6 , CeB 6 and PrB 6 are topologically trivial metal.