Connection of a topological surface state with the bulk continuum in Sb(2)Te(3)(0001).

The surface state of a Z(2) topological insulator connects with the conduction and valence band continua of the bulk, thereby bridging the band gap of the volume. We investigate this connection of the surface and bulk electronic structure for Sb(2)Te(3)(0001) by photoemission experiments and calculations. Upon crossing the topmost valence band the topological surface state (TSS) maintains a coherent spectral signature, a two-dimensional character, and a linear dispersion relation. Surface-bulk coupling manifests itself in the spectra through (i) a characteristic kink in the TSS dispersion as it crosses the topmost valence band and (ii) the appearance of hybridization gaps between the TSS and bulk-derived surface resonance states at higher binding energies. The findings provide a natural explanation for the unexpectedly weak surface-bulk mixing indicated by recent transport experiments on Sb(2)Te(3).