Defect-induced negative magnetoresistance and surface state robustness in the topological insulator BiSbTeSe2

Absence of backscattering and occurrence of weak antilocalization are two characteristic features of topological insulators. We find that the introduction of defects results in the appearance of a negative contribution to magnetoresistance (MR) in the topological insulator BiSbTeSe2 at temperatures below 50 K. Our analysis shows that the negative MR originates from an increase in the density of defect states created by the introduction of disorder, which leaves the surface states unaffected. We find a decrease in the magnitude of the negative MR contribution with increasing temperature and a robustness of the topological surface states to external disorder.