Band Symmetries of Mixed-Valence Topological Insulator: SmB₆

Abstract

We have investigated the band structure and the band symmetry of\nmixed-valence insulator SmB$_{6}$ systematically within the density functional\ntheory (DFT). We have analyzed the symmetries and characters of Sm $4f$ and\n$5d$ bands near the Fermi level ($E_F$) in terms of the non-relativistic real\ncubic bases as well as the relativistic complex bases incorporating the\nspin-orbit coupling and the cubic crystal field. Further, we have found that\nthe semi-core band located at $\\sim 15$ eV below $E_F$ has the mixed parity and\nthereby affects the parity eigenvalues of the special ${\\bf k}$-points\nconsiderably. We have discussed the possible surface states and topological\nclass of SmB$_{6}$, based on the bulk parity tables.\n