Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.
@article{arxiv.1407.2647,
title = {Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6},
author = {W. T. Fuhrman and J. Leiner and P. Nikolić and G. E. Granroth and M. B. Stone and M. D. Lumsden and L. DeBeer-Schmitt and P. A. Alekseev and J. -M. Mignot and S. M. Koohpayeh and P. Cottingham and W. Adam Phelan and L. Schoop and T. M. McQueen and C. Broholm},
journal= {arXiv preprint arXiv:1407.2647},
year = {2015}
}