  We performed angle-resolved photoelectron spectroscopy of the Bi(111) surface
to demonstrate that this surface support edge states of non-trivial topology.
Along the $\bar{\Gamma}\bar{M}$-direction of the surface Brillouin zone, a
surface-state band disperses from the projected bulk valence bands at
$\bar{\Gamma}$ to the conduction bands at $\bar{M}$ continuously, indicating
the non-trivial topological order of three-dimensional Bi bands. We ascribe
this finding to the absence of band inversion at the $L$ point of the bulk Bi
Brillouin zone. According to our analysis, a modification of tight-binding
parameters can account for the non-trivial band structure of Bi without any
other significant change on other physical properties.
