Incomplete protection of the surface Weyl cones of the Kondo insulator SmB6: Spin exciton scattering

Abstract

© 2015 American Physical Society. The compound SmB6 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 SmB6 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.