Topological superfluid phases of an atomic Fermi gas with in- and out-of-plane Zeeman fields and equal Rashba-Dresselhaus spin-orbit coupling

摘要

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