Eur. Phys. J. D (2015) 69: 158
https://doi.org/10.1140/epjd/e2015-60131-7

Regular Article

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

¹ Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, and Istituto Nazionale di Fisica Nucleare, Sezione di Firenze Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
² Frankfurt University of Applied Sciences, Nibelungenplatz 1, 60318 Frankfurt am Main, Germany

^a e-mail: matera@fi.infn.it
^b e-mail: mfwagner@mailaps.org

Received: 26 February 2015
Received in final form: 25 May 2015
Published online: 16 June 2015

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.