Faraday rotation and transmittance as markers of topological phase transitions in 2D materials

TL;DR

This paper investigates how magneto-optical properties like Faraday rotation and transmittance can serve as markers for topological phase transitions in various 2D materials under external fields.

Contribution

It introduces a method to identify topological phase transitions in 2D materials by analyzing magneto-optical responses such as Faraday rotation and transmittance.

Findings

Extremal transmittance and sign change of Faraday angle mark topological phase transitions.

Transmittance minima indicate energy gap closing in non-topological materials.

Magneto-optical properties can be tuned by external fields, chemical potential, and temperature.

Abstract

We analyze the magneto-optical conductivity (and related magnitudes like transmittance and Faraday rotation of the irradiated polarized light) of some elemental two-dimensional Dirac materials of group IV (graphene analogues, buckled honeycomb lattices, like silicene, germanene, stannane, etc.), group V (phosphorene), and zincblende heterostructures (like HgTe/CdTe quantum wells) near the Dirac and gamma points, under out-of-plane magnetic and electric fields, to characterize topological-band insulator phase transitions and their critical points. We provide plots of the Faraday angle and transmittance as a function of the polarized light frequency, for different external electric and magnetic fields, chemical potential, HgTe layer thickness and temperature, to tune the material magneto-optical properties. We have shown that absortance/transmittance acquires extremal values at the critical point, where the Faraday angle changes sign, thus providing fine markers of the topological phase transition. In the case of non-topological materials as phosphorene, a minimum of the transmittance is also observed due to the energy gap closing by an external electric field.