Incomplete protection of the surface Weyl cones of the Kondo insulator ${\mathrm{SmB}}_{6}$: Spin exciton scattering

Incomplete protection of the surface Weyl cones of the Kondo insulator ${SmB}_{6}$ : Spin exciton scattering

G. A. Kapilevich, P. S. Riseborough, A. X. Gray, M. Gulacsi, Tomasz Durakiewicz, and J. L. Smith

Phys. Rev. B 92, 085133 – Published 20 August 2015

Abstract

The compound ${SmB}_{6}$ is a Kondo insulator, where the lowest-energy bulk electronic excitations are spin-excitons. It also has surface states that are subjected to strong spin-orbit coupling. It has been suggested that ${SmB}_{6}$ is also a topological insulator. Here we show that, despite the absence of time-reversal symmetry breaking and the presence of strong spin-orbit coupling, the chiral spin texture of the Weyl cone is not completely protected. In particular, we show that the spin-exciton-mediated scattering produces features in the surface electronic spectrum at energies separated from the surface Fermi energy by the spin-exciton energy. Despite the features being far removed from the surface Fermi energy, they are extremely temperature dependent. The temperature variation occurs over a characteristic scale determined by the dispersion of the spin-exciton. The structures may be observed by electron spectroscopy at low temperatures.