Bose-Einstein condensate of two-dimensional excitons in a ring: Necklace-like modulation of order parameter

TL;DR

This paper theoretically investigates the Bose-Einstein condensation of two-dimensional excitons in a ring, revealing that disorder induces a necklace-like modulation of the condensate's order parameter, which may explain experimental observations.

Contribution

It derives a nonlinear Gross-Pitaevskii equation for exciton BEC in a ring with disorder and demonstrates necklace-like structures in the ground state.

Findings

Necklace-like modulation appears due to disorder and nonlinearity.

The structure remains stable in the Bose-Einstein condensate phase.

Results align with recent experimental photoluminescence observations.

Abstract

We have studied theoretically the Bose-Einstein condensation (BEC) of two-dimensional excitons in a ring with small random width variation. We derive a nonlinear Gross-Pitaevkii equation (GPE) for such a condensate. Our numerical solution of the ground state of the GPE displays a necklace-like structure in the presence of small random variation of ring width. This is a consequence of the interplay between random potential and the nonlinear repulsive term of the GPE. Our result suggests that the formation of ring and necklace-like structures observed recently in the photoluminescence of quantum wells may be stable even in the BEC phase.