Topological quantization in units of the fine structure constant

TL;DR

This paper proposes an optical experiment to directly measure the quantized topological magnetoelectric effect in three-dimensional topological insulators, providing a new way to observe fundamental topological phenomena in condensed matter physics.

Contribution

It introduces a novel optical measurement method to detect the topological magnetoelectric effect quantized by the fine structure constant, independent of material specifics.

Findings

Proposes an optical experiment to measure topological quantization.

Enables independent measurement of surface Hall conductances.

Provides a direct observation method for topological phenomena.

Abstract

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 $\alpha=e^2/\hbar c$. 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.