Linear magnetoresistance and surface to bulk coupling in topological insulator thin films

TL;DR

This study investigates the temperature-dependent magnetoresistance in topological insulator thin films, revealing a non-saturating linear magnetoresistance caused by surface-bulk coupling, with potential for estimating this coupling strength.

Contribution

It introduces a model explaining linear magnetoresistance as a result of surface and bulk conduction channel competition, linking the crossover field to surface-bulk coupling strength.

Findings

Linear magnetoresistance observed at high magnetic fields.

Crossover field decreases with increasing temperature.

Surface-bulk coupling strength can be estimated from the crossover field.

Abstract

We explore the temperature dependent magnetoresistance of bulk insulating topological insulator thin films. Thin films of Bi2Se2Te and BiSbTeSe1.6 were grown using Pulsed Laser Deposition technique and subjected to transport measurements. Magnetotransport measurements indicate a non-saturating linear magnetoresistance (LMR) behavior at high magnetic field values. We present a careful analysis to explain the origin of LMR taking into consideration all the existing models of LMR. Here we consider that the bulk insulating states and the metallic surface states constitute two parallel conduction channels. Invoking this, we were able to explain linear magnetoresistance behavior as a competition between these parallel channels. We observe that the crossover field, where LMR sets in, decreases with increasing temperature. We propose that this cross over field can be used phenomenologically to estimate the strength of surface to bulk coupling.