Thin topological insulator film in a perpendicular magnetic field

TL;DR

This study investigates the Landau level spectrum and quantum phase transitions in ultrathin topological insulator films under perpendicular magnetic fields, considering hybridization and spin effects.

Contribution

It provides a detailed calculation of Landau levels in hybridized topological insulator films, revealing a field-driven quantum phase transition between distinct Hall states.

Findings

Identified a quantum phase transition driven by magnetic field strength.

Calculated the full Landau level spectrum including hybridization and Zeeman effects.

Demonstrated the transition between zero and quantized Hall conductivity states.

Abstract

We report on a study of an ultrathin topological insulator film with hybridization between the top and bottom surfaces, placed in a quantizing perpendicular magnetic field. We calculate the full Landau level spectrum of the film as a function of the applied magnetic field and the magnitude of the hybridization matrix element, taking into account both the orbital and the Zeeman spin splitting effects of the field. For an undoped film, we find a quantum phase transition between a state with a zero Hall conductivity and a state with a quantized Hall conductivity equal to $e^2/h$, as a function of the magnitude of the applied field. The transition is driven by the competition between the Zeeman and the hybridization energies.