The ground state of polaron in an ultracold dipolar Fermi gas

TL;DR

This paper investigates the ground-state properties of Fermi polarons in a three-dimensional dipolar Fermi gas, revealing anisotropic effects and how dipole-dipole interactions influence polaron characteristics at unitarity.

Contribution

It introduces a variational approach to analyze anisotropic polaron properties in a dipolar Fermi gas, highlighting the impact of dipole-dipole interactions on effective mass and drag parameters.

Findings

Transverse effective mass decreases by ~10% with increasing DDI.

Transverse momentum drag parameter decreases by ~10% with increasing DDI.

Longitudinal properties show weak dependence on DDI.

Abstract

An impurity atom immersed in an ultracold atomic Fermi gas can form a quasiparticle, so-called Fermi polaron, due to impurity-fermion interaction. We consider a three-dimensional homogeneous dipolar Fermi gas as a medium, where the interatomic dipole-dipole interaction (DDI) makes the Fermi surface deformed into a spheroidal shape, and, using a Chevy-type variational method, investigate the ground-state properties of the Fermi polaron: the effective mass, the momentum distribution of a particle-hole (p-h) excitation, the drag parameter, and the medium density modification around the impurity. These quantities are shown to exhibit spatial anisotropies in such a way as to reflect the momentum anisotropy of the background dipolar Fermi gas. We have also given numerical results for the polaron properties at the unitarity limit of the impurity-fermion interaction in the case in which the impurity and fermion masses are equal. It has been found that the transverse effective mass and the transverse momentum drag parameter of the polaron both tend to decrease by $ \sim 10\%$ when the DDI strength is raised from $0$ up to around its critical value, while the longitudinal ones exhibit a very weak dependence on the DDI.