Superradiant coupling effects in transition-metal dichalcogenides

TL;DR

This study investigates superradiant coupling in layered transition-metal dichalcogenides, revealing nonmonotonous transmission behavior with layer number and confirming superradiance as the cause through experiments and microscopic calculations.

Contribution

It provides the first experimental evidence of superradiant effects in layered TMDs and demonstrates their impact on optical transmission properties.

Findings

Transmission at exciton resonance does not saturate in thick samples

Transmission varies nonmonotonously with layer number

Microscopic calculations confirm superradiant coupling as the cause

Abstract

Cooperative effects allow for fascinating characteristics in light-matter interacting systems. Here, we study naturally occurring superradiant coupling in a class of quasi-two-dimensional, layered semiconductor systems. We perform optical absorption experiments of the lowest exciton for transition-metal dichalcogenides with different numbers of atomic layers. We examine two representative materials, MoSe$_2$ and WSe$_2$, using incoherent broadband white light. The measured transmission at the A exciton resonance does not saturate for optically thick samples consisting of hundreds of atomic layers, and the transmission varies nonmonotonously with the layer number. A self-consistent microscopic calculation reproduces the experimental observations, clearly identifying superradiant coupling effects as the origin of this unexpected behavior.