Dynamic structure factor of Fermi superfluid in the BEC-BCS crossover

TL;DR

This paper derives the low-energy excitation spectrum and dynamic structure factor of a cigar-shaped Fermi superfluid across the BEC-BCS crossover, providing insights for experimental Bragg spectroscopy measurements.

Contribution

It introduces a polytropic equation of state-based model to analyze multibranch bosonic excitations and calculates the dynamic structure factor in different crossover regimes.

Findings

Dynamic structure factor varies across BEC-BCS regimes.

Bragg spectroscopy can probe multibranch excitations.

Momentum transfer predictions for Bragg pulses.

Abstract

We consider cigar shaped Fermi superfluid in the BEC-BCS crossover. Using polytropic form of equation of state, we derive low energy multibranch bosonic excitations and the corresponding density fluctuations in three different regimes along the crossover, namely weak-coupling BCS, unitarity and molecular BEC regimes. Bragg spectroscopy can be used to probe the multibranch nature of the low energy bosonic excitations by measuring dynamic structure factor. Therefore, we calculate dynamic structure factor in those three different regimes. In the Bragg spectroscopy, an actual observable is momentum imparted to the superfluid due to the Bragg potential. We also present results of the momentum imparted to the superfluid due to the Bragg pulses.