Density fluctuation effects on the exciton condensate in double layer graphene

TL;DR

This paper investigates how density fluctuations and charge inhomogeneity affect the stability and observability of exciton condensates in double layer graphene, highlighting the importance of the excitonic gap and experimental methods like Coulomb drag.

Contribution

It provides a theoretical analysis of exciton condensate robustness against density fluctuations using mean-field equations and phenomenological models, informing experimental detection strategies.

Findings

Stability depends strongly on the size of the excitonic gap.

Transport experiments like Coulomb drag are promising for observing the condensate.

Density fluctuations can significantly impact the percolation of exciton current.

Abstract

We describe the robustness of an excitonic condensate in double layer graphene against layer density fluctuations and the associated charge inhomogeneity, and discuss the implications for observing the condensate under current experimental conditions. We solve the mean-field equations for a finite imbalance in the Fermi energies in each layer and utilize the results in two phenomenological models for inhomogeneity. We find that the stability of the excitonic condensate against density fluctuations is strongly dependent on the size of the excitonic gap, and that transport experiments (such as Coulomb drag) which rely on percolation of the exciton current through the inhomogeneous sample are promising methods for observing the condensate.