Magnetostriction and exchange effects in trapped dipolar Bose and Fermi gases

TL;DR

This paper investigates how dipolar Bose and Fermi gases in harmonic traps exhibit magnetostrictive distortions in position and momentum space, highlighting differences caused by exchange interactions and providing theoretical predictions for experimental verification.

Contribution

It introduces a detailed analysis of magnetostriction effects in dipolar gases, emphasizing the contrasting momentum space distortions between Bose and Fermi systems and offering analytic approximations.

Findings

Position space magnetostriction is similar in Bose and Fermi gases.

Momentum space magnetostriction differs: Bose and Fermi gases distort oppositely.

Predictions are made for experimental observation in ultra-cold polar molecules.

Abstract

We examine the magnetostrictive position and momentum space distortions that occur in harmonically confined dipolar Bose and Fermi gases. Direct interactions give rise to position space magnetostriction and exchange interactions give rise to momentum space magnetostriction. While the position space magnetostriction is similar in Bose and Fermi systems, the momentum space magnetostriction is markedly different: the Bose gas momentum distribution distorts in the opposite sense to that of the Fermi gas. By relating exchange effects to short range correlations between the particles we discuss the energetic origin of this difference. Our main calculations are based on Hartree-Fock theory, but we also provide analytic approximations for the magnetostriction effects at zero and finite temperature. Our predictions should be verifiable in current experiments with ultra-cold polar molecules.