Surface-induced positive planar Hall effect in topological Kondo insulator SmB6 microribbons

Whether the surface states in SmB6 are topological is still a critical issue in the field of topological Kondo insulators. In the magneto-transport study of single crystalline SmB6 microribbons, we have revealed a positive planar Hall effect (PHE), the amplitude of which increases dramatically with decreasing temperatures but saturates below 5 K. This positive PHE is ascribed to the surface states of SmB6 and expected to arise from the anisotropy in lifting the topological protection from back-scattering by the in-plane magnetic field, thus suggesting the topological nature of surface states in SmB6. On the contrary, a negative PHE is observed for the bulk states at high temperatures, which is almost three orders of magnitudes weaker than the surface-induced positive PHE.