Correlation between changeover from weak antilocalization (WAL) to weak localization (WL) and positive to negative magnetoresistance in S-doped Bi_1.5Sb_0.5Te_1.3Se_1.7

The magneto-transport and angle-resolved photoelectron spectroscopy (ARPES) of the S-doped Bi1.5Sb0.5Te1.3Se1.7 system have been investigated. Both the positive magnetoresistance (pMR) and negative magnetoresistance (nMR) under a perpendicular magnetic field as well as a changeover from weak antilocalization (WAL) to weak localization (WL) are observed. The interplay between pMR and nMR is elucidated in terms of the dephasing and spin–orbit scattering time scales. The topological surface state bands have been explored using ARPES.