Magneto-Optical Conductivity of Silicene and Other Buckled Honeycomb Lattices

TL;DR

This paper investigates the magneto-optical properties of silicene and similar materials, demonstrating how external electric fields and doping influence their electronic transitions and enabling potential experimental verification of topological phases.

Contribution

It provides a detailed theoretical analysis of magneto-optical responses in silicene, highlighting tunable interband transitions and spin-valley polarization effects under external fields and doping.

Findings

Electric field tunes interband transition energies.

Onset frequency of absorption peaks varies between topological and band insulator regimes.

Charge doping induces spin- and valley-polarized responses and shifts spectral weight to intraband transitions.

Abstract

The magneto-optical longitudinal, transverse Hall and circularly-polarized response of silicene and other materials described by a Kane-Mele Hamiltonian are calculated. Particular attention is paid to the effects of an external electric field and finite charge doping. The energy of interband transitions can be tuned by varying the electric field. The onset frequency of the absorptive peaks moves differently between the topological insulator and band insulator regimes. This may be used to verify experimentally the existence of the two insulating phases as well as provide a measure of the spin-orbit band gap. The zeroth Landau level splits between four spin and valley distinct energies resulting in valley-spin-polarized levels in the density of states. With charge doping, transitions between these levels allow for a spin- and valley-polarized response in the conductivity whereby charge carriers of specific spin and valley index can be isolated by tuning the incident photon frequency. Increasing the chemical potential is shown to redistribute spectral weight from interband transitions to a strong low-energy intraband response. For large chemical potential, this intraband feature is associated with the semiclassical cyclotron resonance frequency which is shown to linearly increase with magnetic field.