  The recent experimental realization of synthetic spin-orbit coupling (SOC)
opens a new avenue for exploring novel quantum states with ultracold atoms.
However, in experiments for generating two-dimensional SOC (e.g., Rashba type),
a perpendicular Zeeman field, which opens a band gap at the Dirac point and
induces many topological phenomena, is still lacking. Here we theoretically
propose and experimentally realize a simple scheme for generating two-dimension
SOC and a perpendicular Zeeman field simultaneously in ultracold Fermi gases by
tuning the polarization of three Raman lasers that couple three hyperfine
ground states of atoms. The resulting band gap opening at the Dirac point is
probed using spin injection radio-frequency spectroscopy. Our observation may
pave the way for exploring topological transport and topological superfluids
with exotic Majorana and Weyl fermion excitations in ultracold atoms.
