  We use spin- and angle-resolved photoemission spectroscopy (SARPES) combined
with polarization-variable laser and investigate the spin-orbit coupling effect
under interband hybridization of Rashba spin-split states for the surface
alloys Bi/Ag(111) and Bi/Cu(111). In addition to the conventional band mapping
of photoemission for Rashba spin-splitting, the different orbital and spin
parts of the surface wavefucntion are directly imaged into energy-momentum
space. It is unambiguously revealed that the interband spin-orbit coupling
modifies the spin and orbital character of the Rashba surface states leading to
the enriched spin-orbital entanglement and the pronounced momentum dependence
of the spin-polarization. The hybridization thus strongly deviates the spin and
orbital characters from the standard Rashba model. The complex spin texture
under interband spin-orbit hybridyzation proposed by first-principles
calculation is experimentally unraveled by SARPES with a combination of p- and
s-polarized light.
