Optical activity in chiral stacks of 2D semiconductors

TL;DR

This paper demonstrates that chiral stacks of 2D semiconductors exhibit optical activity and circular dichroism, with resonant enhancement at exciton modes, and predicts circularly polarized photoluminescence.

Contribution

It develops a microscopic theory for optical activity in chiral 2D semiconductor stacks, accounting for exciton spin-dependent hopping and electromagnetic coupling, which is novel.

Findings

Optical activity and circular dichroism are resonantly enhanced at exciton modes.

Circularly polarized photoluminescence is predicted in chiral stacks.

The theory applies to realistic materials like transition metal dichalcogenides.

Abstract

We show that the stacks of two-dimensional semiconductor crystals with the chiral packing exhibit optical activity and circular dichroism. We develop a microscopic theory of these phenomena in the spectral range of exciton transitions which takes into account the spin-dependent hopping of excitons between the layers in the stack and the interlayer coupling of excitons via electromagnetic field. For the stacks of realistic two-dimensional semiconductors such as transition metal dichalcogenides, we calculate the rotation and ellipticity angles of radiation transmitted through such structures. The angles are resonantly enhanced at the frequencies of both bright and dark exciton modes in the stack. We also study the photoluminescence of chiral stacks and show that it is circularly polarized.