Dynamic structure function of a cold Fermi gas at unitarity

TL;DR

This paper presents a theoretical analysis of the dynamic structure function of a resonantly interacting Fermi gas at zero temperature, combining many-body theory and Monte Carlo methods to match experimental data.

Contribution

It introduces a novel approach that integrates dynamic many-body theory with diffusion Monte Carlo to accurately describe excitations in strongly correlated Fermi gases.

Findings

Reproduces recent Bragg scattering data in density and spin channels.

Shows BCS regime response similar to ideal Fermi gas.

Identifies dominance of Bose peak in the BEC regime.

Abstract

We present a theoretical study of the dynamic structure function of a resonantly interacting two-component Fermi gas at zero temperature. Our approach is based on dynamic many-body theory able to describe excitations in strongly correlated Fermi systems. The fixed-node diffusion Monte Carlo method is used to produce the ground-state correlation functions which are used as an input for the excitation theory. Our approach reproduces recent Bragg scattering data in both the density and the spin channel. In the BCS regime, the response is close to that of the ideal Fermi gas. On the BEC side, the Bose peak associated with the formation of dimers dominates the density channel of the dynamic response. When the fraction of dimers is large our theory departs from the experimental data, mainly in the spin channel.