Dynamic structure function of a cold Fermi gas at unitarity

G E Astrakharchik,J Boronat,E Krotscheck,T Lichtenegger

doi:10.1088/1742-6596/529/1/012009

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.

Highlights

An impressive advance in realizing and controlling ultracold Fermi gases has permitted to study physical phenomena whose appearance was previously only a matter of speculation [1]
The system evolves from a BCS regime with no bound state (a < 0) to a molecular one (BEC) with a two-body bound state (a > 0), crossing a singular point where |a| → ∞ corresponding to a Fano-Feshbach resonance [6, 7, 8]
The goal of our study is to utilize successful methods stemming from the many-body theory of strongly interacting systems, combining the virtues of Monte Carlo methods and modern diagrammatic many-body theory, in order to study the dynamic structure function of a low–density gas

Summary

Introduction

An impressive advance in realizing and controlling ultracold Fermi gases has permitted to study physical phenomena whose appearance was previously only a matter of speculation [1]. The system evolves from a BCS regime with no bound state (a < 0) to a molecular one (BEC) with a two-body bound state (a > 0), crossing a singular point where |a| → ∞ corresponding to a Fano-Feshbach resonance [6, 7, 8]. This special point is referred to as the unitary limit and is expected to show a number of universal properties.

Objectives

Results

Conclusion