title: Topological quantization in units of the fine structure constant.
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 α=e²/ℏc. In this Letter, 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.
authors.affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Maciejko
authors.forename: Xiao-Liang
authors.initials: XL
authors.lastname: Qi
authors.forename: H Dennis
authors.initials: HD
authors.lastname: Drew
authors.forename: Shou-Cheng
authors.initials: SC
authors.lastname: Zhang