Temperature and impurity effect on parallel field magnetoconductance of bulk insulating topological insulator (Bi_1−xSb_x)₂Te₃

We have performed a systematic parallel field magnetotransport studies of (Bi_1−xSb_x)₂Te₃ to understand the temperature and impurity effect on the interference of bulk conductance on the surface states of highly insulating topologically insulating compound Bi₂Te₃. The compound exhibits a weak antilocalization effect (WAL) at low temperature and low magnetic field. WAL weakens and a weak localization effect is observed to be developed in the compound with the increase in temperature due to the creation of topologically trivial 2D electron gas states. Strong interlayer interference and coupling of bulk carriers with surface states are observed at low temperature. A similar temperature effect is observed for all concentrations of Sb. Topologically protected surface states enhance with the increase in Sb contents up to x  =  0.3; however, a further increase in Sb concentration leads to a decrease in surface states. The data has been analysed via the generalised Altshuler and Aronov model for parallel field transport anticipating weak antilocalization and interlayer interference. (paper)