Eur. Phys. J. D 53, 75-87 (2009)
https://doi.org/10.1140/epjd/e2009-00046-4

LOFF and breached pairing with cold atoms

¹ Department of Physics, Indian Institute of Technology, New, Delhi, 110016, India
² Theory Division, Physical Research Laboratory, Navrangpura, Ahmedabad, 380 009, India
³ School of Physical Sciences, Jawaharlal Nehru University, New Delhi, 110 067, India

Corresponding authors: ^a amruta@physics.iitd.ac.in - ^b hm@prl.res.in

Received: 25 April 2008
Revised: 6 December 2008
Published online: 13 February 2009

Abstract

We investigate here the Cooper pairing of fermionic atoms with mismatched Fermi surfaces using a variational construct for the ground state. We determine the state for different values of the mismatch of chemical potential for weak as well as strong coupling regimes including the BCS BEC cross over region. We consider Cooper pairing with both zero and finite net momentum. Within the variational approximation for the ground state and comparing the thermodynamic potentials, we show that (i) the LOFF phase is stable in the weak coupling regime; (ii) the LOFF window is maximum on the BEC side near the Feshbach resonance; and (iii) the existence of stable gapless states with a single Fermi surface for negative average chemical potential on the BEC side of the Feshbach resonance.