  We construct continuum models of 3D and 4D topological insulators by coupling
spin-1/2 fermions to an SU(2) background gauge field, which is equivalent to a
spatially dependent spin-orbit coupling. Higher dimensional generalizations of
flat Landau levels are obtained in the Landau-like gauge. The 2D helical Dirac
modes with opposite helicities and 3D Weyl modes with opposite chiralities are
spatially separated along the third and fourth dimensions, respectively. Stable
2D helical Fermi surfaces and 3D chiral Fermi surfaces appear on open
boundaries, respectively. The charge pumping in 4D Landau level systems shows
quantized 4D quantum Hall effect.
