Fundamental topological phenomena in condensed matter physics are associated with a quantized electromagnetic response in units of fundamental constants. Recently, it has been predicted theoretically that the time-reversal invariant topological insulator in three dimensions exhibits a topological magnetoelectric effect quantized in units of the fine structure constant α=e2/ℏc. In this work, we propose an optical experiment to directly measure this topological quantization phenomenon, independent of material details. Our proposal also provides a way to measure the half-quantized Hall conductances on the two surfaces of the topological insulator independently of each other.
@article{arxiv.1004.2514,
title = {Topological quantization in units of the fine structure constant},
author = {Joseph Maciejko and Xiao-Liang Qi and H. Dennis Drew and Shou-Cheng Zhang},
journal= {arXiv preprint arXiv:1004.2514},
year = {2018}
}