Beginnings of exciton condensation in coronene analog of graphene double layer

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 computationally examine the beginnings of exciton condensation in a double layer composed 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 Å. Visualization reveals interlayer excitons at the separation distance of the condensate. We determine the exciton population as a function of the twist angle between 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 such as the graphene double layer.

Quantum Many-Body Theory from a Solution of the N -Representability Problem

“…More recently, the author [10] showed that the complete N -representability conditions are derivable from convex combinations of higher-particle, constraint matrices. In the past decade approximate conditions have been employed in variational calculations of the 2-RDM to solve significant problems such as the elucidation of the electronic properties of a glassy, highly conductive amorphous polymer [38] and the revelation of exciton condensation in molecular analogs of double-layer graphene [39][40][41][42] (refer to Refs. [43][44][45][46][47][48] for their use in one-particle RDM functional theories).…”

A Pair of 2D Quantum Liquids: Investigating the Phase Behavior of Indirect Excitons

“…At lower temperatures where quantum statistics dominate, the Mott transition is further facilitated by the favorable exchange interaction between like particles. Additionally, excitons may be regarded as weakly interacting neutral bosons and can thus form Bose–Einstein condensates − (BECs) and superfluid phases . However, the transience of excitons often complicates experimental realization of such quantum phases.…”