Resonant manifestations of chiral excitons in magnetooptical Faraday and Kerr effects in topological insulator film

TL;DR

This paper investigates how chiral excitons on topological insulator surfaces influence magnetooptical effects, revealing their resonant contributions to Hall conductivity and potential for experimental detection.

Contribution

It introduces the concept of chiral excitons' resonant effects on magnetooptical responses in topological insulators, highlighting their unique impact on Faraday and Kerr effects.

Findings

Chiral excitons resonantly enhance Faraday angle and ellipticity.

They decrease Kerr angle and significantly affect ellipticity.

Conditions for experimental observation are discussed.

Abstract

Manifestation of chiral excitons on surfaces of topological insulator thin film with magnetically induced energy gap in the surface spectrum in magnetooptical Kerr and Faraday effects is analyzes. Excitonic contribution to a surface optical conductivity tensor is calculated. Chiral excitons contrary to conventional ones resonantly contribute to Hall conductivity due to lack of the symmetry between the states with opposite angular momentum. They can lead to considerable enhancement of Faraday angle and ellipticity of transmitted electromagnetic wave. Chiral excitons cause decrease of Kerr angle and prominent signatures in ellipticity of reflected electromagnetic wave. Conditions for experimental observation of described effects are discussed.