Breakdown of the strong multiplet description of the Sm ion in the topological Kondo insulator SmB: specific heat studies.

We have theoretically confirmed the existence of in-gap real quantum-mechanical states in SmB, which have been suggested by experiments. These in-gap states, below the hybridization gap of 20 meV, are related to the Sm ion states and can be revealed by calculations within the spin-orbital |LSLS〉 space, with L = 3 and S = 3. Our approach overcomes difficulties related to the singlet J = 0 multiplet ground state.