High-polarization limit of the quasi-two-dimensional Fermi gas

TL;DR

This paper develops a refined theoretical model for highly spin-imbalanced quasi-2D Fermi gases, revealing shifts in polaron-molecule transition points and detailed behaviors of polarons across dimensional crossovers, aligning better with experimental observations.

Contribution

It introduces a theory that extends beyond traditional 2D models to accurately describe quasi-2D Fermi gases under experimental conditions, accounting for many-body effects and confinement.

Findings

Polaron-molecule transition shifts to lower binding energies due to confinement.

Attractive polaron energy exhibits cusps across the 2D-3D crossover.

Repulsive polaron is well-described by a simple 2D interaction parameter.

Abstract

We demonstrate that the theoretical description of current experiments of quasi-2D Fermi gases requires going beyond usual 2D theories. We provide such a theory for the highly spin-imbalanced quasi-2D Fermi gas. For typical experimental conditions, we find that the location of the recently predicted polaron-molecule transition is shifted to lower values of the vacuum binding energy due to the interplay between transverse confinement and many-body physics. The energy of the attractive polaron is calculated in the 2D-3D crossover and displays a series of cusps before converging towards the 3D limit. The repulsive polaron is shown to be accurately described by a 2D theory with a single interaction parameter.