Collective modes of p-wave superfluid Fermi gases in BEC phase

TL;DR

This paper investigates the collective excitation modes of p-wave superfluid Fermi gases in the BEC phase, identifying three distinct low-energy modes and comparing them with spinor Bose condensate excitations.

Contribution

It provides a detailed analysis of collective modes in p-wave superfluid Fermi gases on the BEC side, highlighting the agreement with spinor Bose condensate excitations.

Findings

Identification of three low-energy collective modes: phonon-like, single-particle-like, and gapped.

Confirmation that the $p_x+ip_y$ phase is the lowest energy state in both BCS and BEC regimes.

High-accuracy matching of excitation dispersion relations with those of spinor Bose condensates.

Abstract

The low-energy modes of a superfluid atomic Fermi gas at zero temperature are investigated. The Bose-Einstein-condensate (BEC) side of the superfluid phase is studied in detail. The atoms are assumed to be in only one internal state, so that for a sufficiently diluted gas the pairing of fermions can be considered effective in the l=1 channel only. In agreement with previous works on p-wave superfluidity in Fermi systems, it is found that the $p_x+ip_y$ phase represents the lowest energy state in both the Bardeen-Cooper-Schrieffer (BCS) and BEC sides. Our calculations show that at low energy three branches of collective modes can emerge, with different species of dispersion relations: a phonon-like mode, a single-particle-like mode and a gapped mode. A comparison with the Bogoliubov excitations of the corresponding spinor Bose condensate is made. They reproduce the dispersion relations of the excitation modes of the p-wave superfluid Fermi gas to a high accuracy.