title: Superfluidity enhanced by spin-flip tunnelling in the presence of a magnetic field.
abstract: It is well-known that when the magnetic field is stronger than a critical value, the spin imbalance can break the Cooper pairs of electrons and hence hinder the superconductivity in a spin-singlet channel. In a bilayer system of ultra-cold Fermi gases, however, we demonstrate that the critical value of the magnetic field at zero temperature can be significantly increased by including a spin-flip tunnelling, which opens a gap in the spin-triplet channel near the Fermi surface and hence reduces the influence of the effective magnetic field on the superfluidity. The phase transition also changes from first order to second order when the tunnelling exceeds a critical value. Considering a realistic experiment, this mechanism can be implemented by applying an intralayer Raman coupling between the spin states with a phase difference between the two layers.
authors.affiliation: Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Jun-Hui
authors.initials: JH
authors.lastname: Zheng
authors.affiliation: Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan.|Physics Division, National Center for Theoretical Sciences, Hsinchu, 30013, Taiwan.
authors.forename: Daw-Wei
authors.initials: DW
authors.lastname: Wang
authors.affiliation: Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio Ave. 9, Vilnius, 10222, Lithuania.
authors.forename: Gediminas
authors.initials: G
authors.lastname: Juzeliūnas