Excitonic condensation in spatially separated one-dimensional systems

TL;DR

This paper theoretically demonstrates that excitons can form and condense in spatially separated one-dimensional systems, with potential for experimental detection in nanowire structures under optimal conditions.

Contribution

It introduces a mean-field BCS theory for excitonic quasicondensation in 1D systems and provides estimates for excitonic gaps in nanowire geometries.

Findings

Excitons can form from separated electron and hole populations in 1D.

Optimal pairing conditions include small band overlap, large effective mass, and low dielectric constant.

Excitonic quasicondensation is detectable in nanowires without magnetic fields.

Abstract

We show theoretically that excitons can form from spatially separated one-dimensional ground state populations of electrons and holes, and that the resulting excitons can form a quasicondensate. We describe a mean-field Bardeen-Cooper-Schrieffer theory in the low carrier density regime and then focus on the core-shell nanowire giving estimates of the size of the excitonic gap for InAs/GaSb wires and as a function of all the experimentally relevant parameters. We find that optimal conditions for pairing include small overlap of the electron and hole bands, large effective mass of the carriers, and low dielectric constant of the surrounding media. Therefore, one-dimensional systems provide an attractive platform for the experimental detection of excitonic quasicondensation in zero magnetic field.