Any axion insulator must be a bulk three-dimensional topological insulator

Abstract

This study demonstrates that, contrary to earlier claims in the field involving analyses of a so-called ``zero Hall plateau'', it is more intricate than expected to unambiguously reveal the existence of an axion insulator. In particular, the authors find from their scaling analysis of transport experiments on V-doped (Bi,Sb)${}_{2}$Te${}_{3}$ films of varying thickness that the truly three-dimensional bulk character is a necessary condition for axion insulators, a condition that is likely not satisfied for the materials exhibiting a zero Hall plateau.