Peter Riseborough

Temple University, Philadelphia
Spin Exciton Scattering and Resonant Structure in the Surface Density of States in SmB6, a possible topologic Insulator

The compound SmB6 is a Kondo Insulator, where the lowest-energy bulk electronic excitations are spin excitons. A spin exciton is an excitation of an enhanced Pauli paramagnetic material which has an excitation energy smaller than the semiconducting gap. The spin exciton energy is very sharp since the excitation cannot decay into electron hole pairs. SmB6 also has surface states that are subjected to strong spin-orbit coupling. It has also been suggested that SmB6 is 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 have been observed by electron spectroscopy at low temperatures and by inelastic planer tunneling.

Institut Quantique
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