Incomplete Protection of the Surface Weyl Cones of the Kondo Insulator SmB$_6$: Spin Exciton Scattering

TL;DR

This paper investigates how spin exciton scattering affects the surface Weyl cones in the Kondo insulator SmB$_6$, revealing incomplete topological protection and temperature-dependent spectral features observable via electron spectroscopy.

Contribution

It demonstrates that spin-exciton mediated scattering partially breaks the protection of surface Weyl cones in SmB$_6$, highlighting the role of spin excitons in surface state dynamics.

Findings

Surface states show features at energies related to spin-exciton energy.

Features are highly temperature-dependent, influenced by spin-exciton dispersion.

Surface Weyl cone protection is incomplete despite strong spin-orbit coupling.

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.