Sound velocity and multibranch Bogoliubov spectrum of an elongated Fermi superfluid in the BEC-BCS crossover

TL;DR

This paper investigates the excitation spectrum and sound velocity of an elongated Fermi superfluid across the BEC-BCS crossover, providing analytic expressions and discussing experimental measurement prospects.

Contribution

It offers new analytic formulas for sound velocity and detailed multibranch Bogoliubov spectra in elongated Fermi superfluids across the crossover.

Findings

Derived analytic expressions for sound velocity.

Presented the complete axial quasiparticle spectrum.

Discussed experimental measurement feasibility.

Abstract

We study properties of excited states of an elongated Fermi superfluid along the BEC-BCS crossover including the unitarity limit. Analytic expressions for the sound velocity in an inhomogeneous as well as homogeneous Fermi superfluid along the crossover are obtained on the basis of the hydrodynamic theory. The complete excitation spectrum of axial quasiparticles with various discrete radial nodes are presented. We discuss the feasibility of measuring the sound velocity and the multibranch Bogoliubov spectrum experimentally.