Bound states and Cooper pairs of molecules in 2D optical lattices bilayer

TL;DR

This paper explores how ultra-cold dipolar Fermi molecules in a 2D optical lattice bilayer form bound states and Cooper pairs, revealing conditions that favor pairing and providing insights into BCS-BEC crossover superfluidity.

Contribution

It introduces a variational approach to analyze bound states and Cooper pairs in 2D lattice bilayers, including an analytic dimer-dimer interaction in the BEC regime, advancing understanding of superfluidity in dipolar gases.

Findings

Zero center mass momentum bound states are favored by 2D confinement.

Maximum binding energies depend on layer populations and pair momentum.

Analytic expression for dimer-dimer interaction in deep BEC regime.

Abstract

We investigate the formation of Cooper pairs, bound dimers and the dimer-dimer elastic scattering of ultra- cold dipolar Fermi molecules confined in a 2D optical lattice bilayer configuration. While the energy and their associated bound states are determined in a variational way, the correlated two-molecule pair is addressed as in the original Cooper formulation. We demonstrate that the 2D lattice confinement favors the formation of zero center mass momentum bound states. Regarding the Cooper pairs binding energy, this depends on the molecule populations in each layer. Maximum binding energies occur for non-zero (zero) pair momentum when the Fermi system is polarized (unpolarized). We find an analytic expression for the dimer-dimer effective interaction in the deep BEC regime. The present analysis represents a route for addressing the BCS-BEC crossover superfluidity in dipolar Fermi gases confined in 2D optical lattices within the current experimental panorama.