# Superfluidity in density imbalanced bilayers of dipolar fermions

## TL;DR

This paper explores the phase diagram of an imbalanced bilayer of dipolar fermions at zero temperature, revealing conditions for stable superfluid phases and the effects of density imbalance and layer spacing.

## Contribution

It provides a theoretical analysis of superfluid phases in dipolar fermion bilayers considering population imbalance, layer spacing, and intralayer screening effects, which was not previously detailed.

## Key findings

- Density imbalance reduces the pairing gap.
- Stable homogeneous superfluidity occurs when dipolar length exceeds layer spacing.
- Inhomogeneous superfluid phases survive with intralayer screening effects.

## Abstract

We study the zero temperature phase diagram of an imbalanced bilayer of dipolar fermions. We consider perpendicularly aligned identical dipoles in two layers and investigate the effect of population imbalance on the ground state phase at different layer spacings and average densities. The attractive part of the interlayer interaction could lead to the BEC-BCS crossover and the Fermi surface mismatch between two layers results in interesting uniform and nonuniform superfluid phases, which we have investigated here using the BCS mean-field theory together with the superfluid-mass density criterion. The density imbalance reduces the pairing gap. At low densities, where the system is on the BEC side of the crossover, this reduction is quite smooth while a dense system rapidly becomes normal at intermediate density polarizations. Stable homogeneous superfluidity is predicted to appear on the phase diagram when the dipolar length exceeds both the layer spacing and the average intralayer distance between dipoles, a regime which should be readily accessible experimentally. This homogeneous superfluid phase becomes unstable at intermediate densities and layer spacings. We have also examined that these uniform and inhomogeneous superfluid phases survive when the effects of intralayer screenings are also incorporated in the formalism.