Effects of density imbalance on the BCS-BEC crossover in semiconductor electron-hole bilayers

TL;DR

This paper investigates how density imbalance affects the BCS-BEC crossover in semiconductor electron-hole bilayers, revealing phase diagram asymmetries and criteria for superfluidity onset.

Contribution

It introduces an analysis of density imbalance effects on the BCS-BEC crossover and proposes a new criterion for superfluidity onset based on chemical potential jumps.

Findings

Identified phase diagram crossover from BCS to BEC regimes.

Analyzed effects of independent electron and hole density variations.

Proposed chemical potential jump as a superfluidity criterion.

Abstract

We study the occurrence of excitonic superfluidity in electron-hole bilayers at zero temperature. We not only identify the crossover in the phase diagram from the BCS limit of overlapping pairs to the BEC limit of non-overlapping tightly-bound pairs but also, by varying the electron and hole densities independently, we can analyze a number of phases that occur mainly in the crossover region. With different electron and hole effective masses, the phase diagram is asymmetric with respect to excess electron or hole densities. We propose as the criterion for the onset of superfluidity, the jump of the electron and hole chemical potentials when their densities cross.