Peter Riseborough, Professor of Physics, Temple University, 1925 N. 12th Street, Philadelphia, PA 19122, USA.

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.

Site web du groupe de Pr Riseborough

Cette conférence est présentée par le RQMP Versant Nord du Département de physique de l'Université de Montréal et le Département de génie physique de Polytechnique Montréal.