Renormalized atomic interaction and quadrupole excitations of cold Fermi gas near Feshbach resonance

TL;DR

This paper models quadrupole excitations in cold Fermi gases near Feshbach resonance, using a renormalized interaction approach that captures experimental spectral features.

Contribution

It introduces a renormalized atomic interaction derived from ladder diagrams, improving the understanding of excitation spectra near Feshbach resonances.

Findings

Reproduces the abrupt rise in excitation spectrum observed experimentally.

Accurately predicts large decay widths associated with excitations.

Provides a consistent theoretical framework for quadrupole excitations in cold Fermi gases.

Abstract

We present a model space particle-hole Green's function calculation for the quadrupole excitations of cold Fermi gas near Feshbach resonance using a simple model where atoms are confined in a harmonic oscillator potential. Both the Tamm-Dancoff and random phase approximations are employed. By summing up exactly the ladder diagrams between a pair of interacting atoms to all orders, we obtain a renormalized atomic interaction which has well defined and identical limits as the scattering length tends to $\pm \infty$. The experimentally observed abrupt rise in the excitation spectrum and its associated large decay width are satisfactorily reproduced by our calculation.