The Topological Kondo Insulator SmB6: Surface States and Bulk Spin Excitons
Abstract: Samarium hexaboride (SmB6), a well-known Kondo insulator in which the insulating behavior of the bulk arises from strong electron correlations, has recently attracted great attention owing to its possible topological nature. Although there is strong evidence for this, corroborative spectroscopic evidence was lacking; unlike in the weakly correlated counterparts (e.g., Bi2Se3). Our planar tunneling spectroscopy results reveal the linear density of states as expected for Dirac cones. The energy and temperature dependence indicate that the topological surface states are not protected above a certain temperature and energy range, and we invoke an inelastic tunneling model involving spin excitons that accounts for the observed behavior.