Weak antilocalization in topological insulator Bi₂Te₃ microflakes

We have studied the carrier transport in two topological insulator (TI) Bi₂Te₃ microflakes between 0.3 and 10 K and under applied backgate voltages (V_BG). Logarithmic temperature dependent resistance corrections due to the two-dimensional electron-electron interaction effect in the presence of weak disorder were observed. The extracted Coulomb screening parameter is negative, which is in accord with the situation of strong spin-orbit scattering as is inherited in the TI materials. In particular, positive magnetoresistances (MRs) in the two-dimensional weak-antilocalization (WAL) effect were measured in low magnetic fields, which can be satisfactorily described by a multichannel-conduction model. Both at low temperatures of T<1 K and under high positive V_BG, signatures of the presence of two coherent conduction channels were observed, as indicated by an increase by a factor of ≈2 in the prefactor which characterizes the WAL MR magnitude. Our results are discussed in terms of the (likely) existence of the Dirac fermion surface states, in addition to the bulk states, in the three-dimensional TI Bi₂Te₃ material.