2006/04/30 by Lianyi He, Meng Jin, Pengfei Zhuang
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #Physics of Superconductivity and Magnetism #cond-mat.supr-con #nucl-th #physics.atom-ph
paper · pdf · doi:10.1103/physrevb.74.024516
published as Phys.Rev. B74 (2006) 024516 · 13 pages, 2 figures, published version, erratum will appear soon
openalex publication_date 2006/07/24 · arxiv created 2006/09/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Fermion Cooper pairing with unequal masses is investigated in a standard field theory approach. We derived the superfluid density and Meissner mass squared of the U(1) gauge field in a general two-species model and found that the often used proportional relation between the two quantities is broken when the fermion masses are unequal. In the weak-coupling region, the superfluid density is always negative but the Meissner mass squared becomes mostly positive when the mass ratio between the pairing fermions is large enough. We established a proper momentum configuration of the LOFF pairing with unequal masses and showed that the LOFF state is energetically favored due to the negative superfluid density. The single-plane-wave LOFF state is physically equivalent to an anisotropic state with a spontaneously generated superflow. The extension to a finite-range interaction is briefly discussed.