Beginnings of Exciton Condensation in Coronene Analog of Graphene Double Layer

TL;DR

This study computationally investigates the early stages of exciton condensation in a double-layer coronene system, revealing conditions like interlayer distance and twist angle that promote exciton population peaks, suggesting molecular analogs of graphene can host exciton condensates.

Contribution

It provides the first computational evidence of exciton condensation in a coronene double layer, a molecular-scale analog of graphene heterostructures, highlighting the effects of interlayer separation and twist angle.

Findings

Exciton population peaks at around 1.8 at 2 Å interlayer distance.

Interlayer excitons are visualized at the condensate separation.

Magic twist angles enhance exciton condensation.

Abstract

Exciton condensation, a Bose-Einstein condensation of excitons into a single quantum state, has recently been achieved in low-dimensional materials including twin layers of graphene and van der Waals heterostructures. Here we examine computationally the beginnings of exciton condensation in a double layer comprised of coronene, a seven-benzene-ring patch of graphene. As a function of interlayer separation, we compute the exciton population in a single coherent quantum state, showing that the population peaks around 1.8 at distances near 2 \AA. Visualization reveals interlayer excitons at the separation distance of the condensate. We determine the exciton population as a function of the twist angle between the two coronene layers to reveal the magic angles at which the condensation peaks. As with previous recent calculations showing some exciton condensation in hexacene double layers and benzene stacks, the present two-electron reduced-density-matrix calculations with coronene provide computational evidence for the ability to realize exciton condensation in molecular-scale analogs of extended systems like the graphene double layer.