Non-trivial surface-band dispersion on Bi(111)

We performed angle-resolved photoelectron spectroscopy of the Bi(111) surface to demonstrate that this surface supports edge states of non-trivial topology. Along the \bar{\Gamma }\skew3\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 \skew3\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 in other physical properties.