Symmetry-constrained reorganization of Dirac cones in topological insulators by surface modification

Topological insulators possess a symmetry-protected surface spin current, a property highly relevant to spintronics applications. This current arises from gapless spin-polarized surface states. Calculations show that these states can undergo drastic transformations with surface treatment, despite the overall symmetry-based constraints. Specifically, the single Dirac cone at the zone center for the surface states in Bi2Se3 (Bi2Te3) is transformed, upon hydrogen termination, into three Dirac cones at the zone boundary. This trifurcation enhances the surface spin polarization, but leaves the overall topological order invariant.