# Extremely large non-saturating magnetoresistance and ultrahigh mobility due to topological surface states in metallic Bi2Te3 topological insulator

## TL;DR

This study demonstrates that Bi2Te3 topological insulators exhibit extremely large, non-saturating magnetoresistance and ultrahigh mobility primarily due to topological surface states, with effects dependent on charge carrier density.

## Contribution

It provides experimental evidence linking topological surface states to large magnetoresistance and high mobility in Bi2Te3, highlighting their potential for technological applications.

## Key findings

- Large, non-saturating magnetoresistance observed at low carrier density.
- Ultrahigh mobility associated with surface states.
- WAL effects scale with the normal magnetic field component at low carrier density.

## Abstract

Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge carrier concentrations. At low charge carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to topological surface states shows no dependence on the nature (electrons or holes) of the bulk charge carriers. The observations of an extremely large, non-saturating magnetoresistance, and ultrahigh mobility in the samples with lower carrier density further support the presence of surface states. The physical parameters characterizing the WAL effects are calculated using the Hikami-Larkin-Nagaoka formula. At high charge carrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low charge carrier concentrations. The extremely large magnetoresistance and high mobility of topological insulators have great technological value and can be exploited in magneto-electric sensors and memory devices.