Imbalanced Fermi gas in antiparallel magnetic fields

We study a two-dimensional Fermi gas with the finite density imbalance between two spin components of atoms in antiparallel magnetic fields. The antiparallel magnetic fields act on two different spin components of atoms with same magnitude but opposite directions [1]. It was revealed in the absence of magnetic fields that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where the Cooper pairing takes place with nonzero momentum, emerges in the phase diagram of an imbalanced Fermi gas. Therefore, it is an interesting problem to how the antiparallel magnetic fields compete or cooperate with the FFLO state. We investigate the ground-state phase diagram within the mean-field approximation. At the weak-coupling limit, we find that the FF state is stable with compare to the LO state when the chemical potentials of the two components lie right at Landau levels [2].

[1] M. C. Beeler et al., Nature 498, 201 (2013).
[2] Takaaki Anzai and Yusuke Nishida, in preparation.