Parallel field magnetoresistance in topological insulator thin films

TL;DR

This study investigates how the finite thickness of topological insulator thin films affects magnetoresistance in phase coherent transport under parallel magnetic fields, revealing the importance of surface-bulk coupling.

Contribution

It demonstrates that surface and bulk state coupling is essential for understanding magnetoresistance in TI thin films, introducing the {eta} parameter as a potential figure of merit.

Findings

Finite thickness induces observable MR in phase coherent transport.

Surface-bulk coupling is crucial for interpreting MR data.

{eta} parameter may serve as a metric for TI material quality.

Abstract

We report that the finite thickness of three-dimensional topological insulator (TI) thin films produces an observable magnetoresistance (MR) in phase coherent transport in parallel magnetic fields. The MR data of Bi2Se3 and (Bi,Sb)2Te3 thin films are compared with existing theoretical models of parallel field magnetotransport. We conclude that the TI thin films bring parallel field transport into a unique regime in which the coupling of surface states to bulk and to opposite surfaces is indispensable for understanding the observed MR. The {\beta} parameter extracted from parallel field MR can in principle provide a figure of merit for searching TI compounds with more insulating bulk than existing materials.