Complexes of dipolar excitons in layered quasi-two-dimensional nanostructures

TL;DR

This paper derives analytical expressions for the binding energies of neutral and charged exciton complexes in layered quasi-two-dimensional semiconductors, revealing significant binding energies relevant for many-body phenomena.

Contribution

It introduces a configuration space approach to analytically calculate trion and biexciton binding energies as functions of interlayer distance in layered heterostructures.

Findings

Binding energies up to tens of meV for typical interlayer distances.

Trion binding energy exceeds biexciton binding energy.

Results aid understanding of exciton condensation and electron-hole crystallization.

Abstract

We discuss neutral and charged complexes (biexciton and trion) formed by indirect excitons in layered quasi-two-dimensional semiconductor heterostructures. Indirect excitons -- long-lived neutral Coulomb-bound pairs of electrons and holes of different layers -- have been known for semiconductor coupled quantum wells and are recently reported for van der Waals heterostructures such as bilayer graphene and transition metal dichalcogenides. Using the configuration space approach, we derive the analytical expressions for the trion and biexciton binding energies as functions of the interlayer distance. The method captures essential kinematics of complex formation to reveal significant binding energies, up to a few tens of meV for typical interlayer distances ~3-5 A, with the trion binding energy always being greater than that of the biexciton. Our results can contribute to the understanding of more complex many-body phenomena such as exciton Bose-Einstein condensation and Wigner-like electron-hole crystallization in layered semiconductor heterostructures.