Weak antilocalization in topological insulator Bi$_{2}$Te$_{3}$ microflakes

TL;DR

This study investigates weak antilocalization effects in Bi$_{2}$Te$_{3}$ microflakes, revealing two conduction channels and evidence of Dirac surface states through magnetoresistance measurements at low temperatures.

Contribution

It provides experimental evidence of multiple conduction channels and Dirac surface states in Bi$_{2}$Te$_{3}$ microflakes, enhancing understanding of topological insulator transport properties.

Findings

Observation of weak antilocalization in low magnetic fields.

Identification of two coherent conduction channels.

Signatures of Dirac fermion surface states.

Abstract

We have studied the carrier transport in two topological insulator (TI) Bi$_{2}$Te$_{3}$ microflakes between 0.3 and 10 K and under applied backgate voltages ($V_{\rm BG}$). 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 $V_{\rm BG}$, signatures of the presence of two coherent conduction channels were observed, as indicated by an increase by a factor of $\approx$ 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 Bi$_2$Te$_3$ material.