Cyclotron Resonance in Topological Insulators: Non-Relativistic Effects

TL;DR

This paper investigates how a small non-relativistic term in the Hamiltonian affects cyclotron resonance and optical properties of surface states in topological insulators, revealing particle-hole asymmetry and spectral line splitting.

Contribution

It provides a detailed analysis of non-relativistic effects on cyclotron resonance and magneto-optical responses in topological insulators, highlighting their impact on spectral features and particle-hole symmetry.

Findings

Cyclotron frequency and spectral weight are altered by non-relativistic terms.

Particle-hole asymmetry is introduced by the non-relativistic contribution.

Interband magneto-optical lines split into doublets due to non-relativistic effects.

Abstract

The low-energy Hamiltonian used to describe the dynamics of the helical Dirac fermions on the surface of a topological insulator contains a subdominant non-relativistic (Schr\"odinger) contribution. This term can have an important effect on some properties while having no effect on others. The Hall plateaus retain the same relativistic quantization as the pure Dirac case. The height of the universal interband background conductivity is unaltered, but its onset is changed. However, the non-relativistic term leads directly to particle-hole asymmetry. It also splits the interband magneto-optical lines into doublets. Here, we find that, while the shape of the semiclassical cyclotron resonance line is unaltered, the cyclotron frequency and its optical spectral weight are changed. There are significant differences in both of these quantities for a fixed value of chemical potential or fixed doping away from charge neutrality depending on whether the Fermi energy lies in the valence or conduction band.