Transport Properties of Topological Insulators: Band Bending, Bulk Metal-to-Insulator Transition, and Weak Anti-Localization

TL;DR

This paper reanalyzes transport experiments in topological insulators, clarifies the roles of band bending and weak anti-localization, and offers a unified understanding of their bulk and surface conduction properties.

Contribution

It provides a coherent reinterpretation of TI transport data, emphasizing band-bending effects and correcting misconceptions about weak anti-localization.

Findings

Band-bending significantly influences TI transport properties.

Utilizing band-bending can induce a Mott insulating bulk in thin TIs.

Revised understanding of the weak anti-localization effect in TIs.

Abstract

We reanalyze some of the critical transport experiments and provide a coherent understanding of the current generation of topological insulators (TIs). Currently TI transport studies abound with widely varying claims of the surface and bulk states, often times contradicting each other, and a proper understanding of TI transport properties is lacking. According to the simple criteria given by Mott and Ioffe-Regel, even the best TIs are not true insulators in the Mott sense, and at best, are weakly-insulating bad metals. However, band-bending effects contribute significantly to the TI transport properties including Shubnikov de-Haas oscillations, and we show that utilization of this band-bending effect can lead to a Mott insulating bulk state in the thin regime. In addition, by reconsidering previous results on the weak anti-localization (WAL) effect with additional new data, we correct a misunderstanding in the literature and generate a coherent picture of the WAL effect in TIs.