Kohn-Sham approach to Fermi gas superfluidity: the bilayer of fermionic polar molecules

TL;DR

This paper uses Kohn-Sham Density Functional theory to study superfluidity and the BCS-BEC crossover in bilayer fermionic polar molecules, revealing how optical confinement influences superfluid transition temperatures and localization phenomena.

Contribution

It applies an ab initio DFT approach to analyze superfluid properties of dipolar fermionic bilayers, including effects of optical lattice confinement and interlayer coupling.

Findings

Superfluid transition temperature increases with optical potential strength.

Localization of fermions occurs at small interlayer distances, forming composite bosons.

Results at zero temperature agree with Diffusion Monte Carlo simulations.

Abstract

By using a well established 'ab initio' theoretical approach developed in the past to quantitatively study the superconductivity of condensed matter systems, which is based on the Kohn-Sham Density Functional theory, I study the superfluid properties and the BCS-BEC crossover of two parallel bi-dimensional layers of fermionic dipolar molecules, where the pairing mechanism leading to superfluidity is provided by the inter-layer coupling between dipoles. The finite temperature superfluid properties of both the homogeneous system and one were the fermions in each layer are confined by a square optical lattice are studied at half filling conditions, and for different values of the strength of the confining optical potential. The T=0 results for the homogeneous system are found to be in excellent agreement with Diffusion Monte Carlo results. The superfluid transition temperature in the BCS region is found to increase, for a given inter-layer coupling, with the strength of the confining optical potential. A transition occurs at sufficiently small interlayer distances, where the fermions becomes localized within the optical lattice sites in a square geometry with an increased effective lattice constant, forming a system of localized composite bosons. This transition should be signalled by a sudden drop in the superfluid fraction of the system.