Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization

We reanalyze some of the critical transport experiments and provide a coherent understanding of the current generation of topological insulators (Tls). Currently 11 transport studies abound with widely varying claims of the surface and bulk states, often times contradicting each other, and a proper understanding 01 TI transport properties is lacking. According to the simple criteria given by Mott and loffe-Regel, even the best Tls are not true insulators in the Mott sense, and at best, are weakly-insulating bad metals. However, band-bending effects contribute significantly to the 11 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 Tls. (C) 2014 Elsevier Ltd. All rights reserved.