# Magneto-optical properties of topological insulator thin films with broken inversion symmetry

## TL;DR

This paper investigates the optical properties of ultrathin topological insulator films under magnetic fields, highlighting how symmetry breaking and hybridization influence their electronic transitions and phase transitions.

## Contribution

It introduces a comprehensive analysis of how inversion symmetry breaking and hybridization affect the optical response and phase transitions in topological insulator thin films.

## Key findings

- Inversion symmetry breaking causes Landau level crossings and new optical transitions.
- Tuning hybridization and symmetry parameters induces a phase transition detectable via optical conductivity.
- The study provides measurable signatures of topological phase changes in optical responses.

## Abstract

We determine the optical response of ultrathin film topological insulators in the presence of a quantizing external magnetic field taking into account both hybridization between surface states, broken inversion symmetry and explicit time reversal symmetry breaking by the magnetic field. We find that breaking of inversion symmetry in the system, which can be due to interaction with a substrate or electrical gating, results in Landau level crossings which lead to additional optical transition channels that were previously forbidden. We show that by tuning the hybridization and symmetry breaking parameters, a transition from the normal to a topological insulator phase occurs with measurable signatures in both the longitudinal and optical Hall conductivity.