Tunable chirality and circular dichroism of a topological insulator with $ C_{2v} $ symmetry as a function of Rashba and Dresselhaus parameters

TL;DR

This paper demonstrates how a topological insulator with C$_{2v}$ symmetry, influenced by Rashba and Dresselhaus effects, can have tunable circular dichroism, impacting polarization-sensitive device design and quantum information applications.

Contribution

It introduces a model showing how Rashba and Dresselhaus parameters can control circular dichroism in a topological insulator with C$_{2v}$ symmetry, linking it to valley-electronics.

Findings

Circular dichroism varies smoothly with Rashba and Dresselhaus parameters.

Maximum circular dichroism reaches unity near the Dirac cone.

Potential applications in quantum information processing.

Abstract

Polarization-sensitive devices rely on meta-materials to exhibit varying degrees of absorption of light of a given handedness. The chiral surface states of a topological insulator(TI) selectively absorb right and left circularly polarized light in the vicinity of the Dirac cone reaching its maximum of unity at the $ \Gamma $ point. In this letter, we demonstrate that a band gap open TI with C$_{2v}$ symmetry which is represented through a combination of Rashba and Dresselhaus Hamiltonians alters the preferential absorption of left and right circularly polarized light allowing a smooth variation of the circular dichroism(CD). This variation in CD, reflected in a range of positive and negative values is shown to be a function of the Rashba and Dresselhaus coupling parameters. Additionally, we draw a parallel between the varying CD and the emerging field of valley-electronics in transition metal dichalcogenides and note the possibility of the chiral states as a basis toward quantum information processing.