Spin splitted topological surface states in PbBi4Te7

Abstract

The most important feature in topological insulators is the conducting surface states that support back scattered prohibited transport of charge carriers. We report weak antilocalization (WAL) effect in mm size thick PbBi4Te7 single crystal, the transport evidence of the absence of back scattering of the charge carriers. Temperature dependency of phase coherence length is determined from modified Hikami–Larkin–Nagaoka (HLN) fitting of the WAL curves at different temperatures by considering electron–electron and electron–phonon interactions and the fitting parameters reveal two dimensional (2D) origin of the WAL effect, i.e. the presence of the topological surface states. Extracted Hikami pre-factor, α at different temperatures from the modified HLN fitting signifies that the top and bottom surface states in PbBi4Te7 are connected by bulk diffusive region. Shubnikov–de Haas (SdH) oscillations corroborate the presence of two Fermi surfaces DC1 and DC2 (deep buried one inside other) and non-trivial nature of which are confirmed from the observed -shift in Landau-levels fan diagram based on the SdH oscillations. Mobility (µ SdH ) values are determined from the Dingle analysis and are quite above the bulk mobility (µ) estimated from the low field Hall data, ascertaining the surface origin of the SdH oscillations. Surface Landé g-factors are determined from the observed peak splitting in SdH oscillations, attributed to the Zeeman effect and are 4.412 and 3.26 for DC1 and DC2, respectively, and are the consequence of strong spin–orbit coupling of the surface Dirac Fermions.