Thickness dependence of electrical transport: A test for surface conduction in topological insulators

Abstract

Topological insulators have a conducting surface and an insulating bulk. Resistivity, as defined for a three dimensional conductor, should increase linearly with thickness in case of topological insulators. This is because resistivity is proportional to both resistance and thickness, and the surface conductance of a topological insulator should be independent of the thickness of the topological insulator. Thus, operationally, thickness dependence of resistivity could be one of the important tests in determining whether any material is a topological insulator or not. In this work, we have done a meta-analysis of the electrical transport data reported in the literature on topological insulators. However, many of the data do not follow any linear trend with thickness as is expected in the case of topological insulators. Thus we arrive at the conclusion from the existing data in the literature, that all of these materials cannot be considered as true topological insulators.