  Based on the optical Raman lattice technique, we experimentally realize the
Qi-Wu-Zhang model for quantum anomalous Hall phase in ultracold fermions with
two-dimensional (2D) spin-orbit (SO) coupling. We develop a novel protocol of
pump-probe quench measurement to probe, with minimal heating, the resonant spin
flipping on particular quasi-momentum subspace called band-inversion surfaces.
With this protocol we demonstrate the first Dirac-type 2D SO coupling in a
fermionic system, and detect non-trivial band topology by observing the change
of band-inversion surfaces as the two-photon detuning varies. The non-trivial
band topology is also observed by slowly loading the atoms into optical Raman
lattices and measuring the spin textures. Our results show solid evidence for
the realization of the minimal SO-coupled quantum anomalous Hall model, which
can provide a feasible platform to investigate novel topological physics
including the correlation effects with SO-coupled ultracold fermions.
