  We report the detailed electronic structure of WTe$_2$ by high resolution
angle-resolved photoemission spectroscopy. Unlike the simple one electron plus
one hole pocket type of Fermi surface topology reported before, we resolved a
rather complicated Fermi surface of WTe$_2$. Specifically, there are totally
nine Fermi pockets, including one hole pocket at the Brillouin zone center
$\Gamma$, and two hole pockets and two electron pockets on each side of
$\Gamma$ along the $\Gamma$-$X$ direction. Remarkably, we have observed
circular dichroism in our photoemission spectra, which suggests that the
orbital angular momentum exhibits a rich texture at various sections of the
Fermi surface. As reported previously for topological insulators and Rashiba
systems, such a circular dichroism is a signature for spin-orbital coupling
(SOC). This is further confirmed by our density functional theory calculations,
where the spin texture is qualitatively reproduced as the conjugate consequence
of SOC. Since the backscattering processes are directly involved with the
resistivity, our data suggest that the SOC and the related spin and orbital
angular momentum textures may be considered in the understanding of the
anomalous magnetoresistance of WTe$_2$.
