  We report high-resolution spin-resolved photoemission spectroscopy
(Spin-ARPES) measurements on the parent compound Sb of the first discovered 3D
topological insulator Bi{1-x}Sb{x} [D. Hsieh et al., Nature 452, 970 (2008)
Submitted 2007]. By modulating the incident photon energy, we are able to map
both the bulk and (111) surface band structure, from which we directly
demonstrate that the surface bands are spin polarized by the spin-orbit
interaction and connect the bulk valence and conduction bands in a
topologically non-trivial way. A unique asymmetric Dirac surface state gives
rise to a $k$-splitting of its spin polarized electronic channels. These
results complement our previously published works on this materials class and
re-confirm our discovery of first bulk (3D) topological insulator - topological
order in bulk solids. [Invited article for NJP-IOP Focus issue on "Topological
Insulators"]
