4$f$ crystal field ground state of the strongly correlated topological insulator SmB${}_6$

Abstract

We investigated the crystal-electric field ground state of the 4$f$ manifold in the strongly correlated topological insulator SmB${}_6$ using core level non-resonant inelastic x-ray scattering (NIXS). The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the $\hat{I}{“}_8$ quartet state of the Sm $f^5$ $J$=$5/2$ configuration governs the ground-state symmetry and hence the topological properties of SmB${}_6$. Our findings contradict the results of density functional calculations reported so far.

9 pages, 9 figures