Excitons and biexcitons in symmetric electron-hole bilayers

TL;DR

This study uses diffusion quantum Monte Carlo to analyze excitonic and biexcitonic phases in symmetric electron-hole bilayers, revealing phase transitions and the stability of excitons and biexcitons across various densities and layer separations.

Contribution

It introduces a flexible trial wave function for simulating fluid, excitonic, and biexcitonic phases in symmetric electron-hole bilayers, providing detailed phase transition insights.

Findings

Identifies continuous phase transitions among fluid, excitonic, and biexcitonic phases.

Excitons survive down to rs = 0.5 a.u. at zero layer separation.

Biexcitons form at rs > 2.5 a.u.

Abstract

Symmetric electron-hole bilayer systems have been studied at zero temperature using the diffusion quantum Monte Carlo method. A flexible trial wave function is used that can describe fluid, excitonic and biexcitonic phases. We calculate condensate fractions and pair correlation functions for a large number of densities rs and layer separations d. At small d we find a one-component fluid phase, an excitonic fluid phase, and a biexcitonic fluid phase, and the transitions among them appear to be continuous. At d = 0, excitons appear to survive down to about rs = 0.5 a.u., and biexcitons form at rs > 2.5 a.u.