Three-dimensional spin–orbit coupled Fermi gases: Fulde–Ferrell pairing, Majorana fermions, Weyl fermions, and gapless topological superfluidity*
Liu Xia-Jia), Hu Huia), Pu Hanb),c)†
       
Zero temperature phase diagram of a 3D Rashba spin–orbit coupled Fermi gas on the plane of in-plane and out-of-plane Zeeman fields, with a spin–orbit coupling strength λ = E F/ k F and an interaction strength 1/( k F a s) = −0.5. The color map shows the lowest energy in the lower particle branches in units of E F. There are various superfluid phases, as described in detail in the text. The solid line shows the topological phase transition. While the dot-dashed line indicates the transition within the two types of topological superfluids, which have four or two Weyl nodes/loops, respectively. The solid circles are the boundary where the superfluid becomes gapless, apart from the Weyl nodes.