  We analyze the effects of in- and out-of-plane Zeeman fields on the BCS-BEC
evolution of a Fermi gas with equal Rashba-Dresselhaus (ERD) spin-orbit
coupling (SOC). We show that the ground state of the system involves novel
gapless superfluid phases that can be distinguished with respect to the
topology of the momentum-space regions with zero excitation energy. For the
BCS-like uniform superfluid phases with zero center-of-mass momentum, the zeros
may correspond to one or two doubly-degenerate spheres, two or four spheres,
two or four concave spheroids, or one or two doubly-degenerate circles,
depending on the combination of Zeeman fields and SOC. Such changes in the
topology signal a quantum phase transition between distinct superfluid phases,
and leave their signatures on some thermodynamic quantities. We also analyze
the possibility of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like nonuniform
superfluid phases with finite center-of-mass momentum and obtain an even richer
phase diagram.
