We study a two-dimensional Fermi gas with an attractive interaction subjectedto synthetic magnetic fields assumed to be mutually antiparallel for twodifferent spin components. By employing the mean-field approximation, we findthat its phase diagram at zero temperature consists of pair superfluid andquantum spin Hall insulator phases and closely resembles that of theBose-Hubbard model. The resulting two phases are separated by a second-orderquantum phase transition classified into the universality class of either thedilute Bose gas or the XY model. We also show that the pairing gap can beenhanced significantly by the antiparallel magnetic fields as a consequence ofmagnetic catalysis, which may facilitate the realization of the pair superfluidin two dimensions by ultracold atom experiments.
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