  Using a tight-binding description, we show how the zero-dimensional state
bound to the edge of a single one-dimensional helical chain of tellurium atoms
evolves into two-dimensional states on the c-axis surface of the
three-dimensional trigonal bulk. We give an effective Hamiltonian description
of its dispersion in k-space by exploiting confinement to a virtual bilayer,
and elaborate on the diminished role of spin-orbit coupling. These
previously-unidentified intrinsic gap-penetrating surface bands were neglected
in the interpretation of seminal experiments, where two-dimensional transport
was otherwise attributed to extrinsic accumulation layers.
