Tuning Transport Properties of Topological Edge States of Bi(111) Bilayer Film by Edge Adsorption

Based on first-principles and tight-binding calculations, we report that the transport properties of topological edge states of zigzag Bi(111) nanoribbon can be significantly tuned by H edge adsorption. The Fermi velocity is increased by one order of magnitude, as the Dirac point is moved from Brillouin zone boundary to Brillouin zone center and the real-space distribution of Dirac states are made twice more delocalized. These intriguing changes are explained by an orbital filtering effect of edge H atoms, which removes certain components of $p$ orbits of edge Bi atoms that reshapes the topological edge states. In addition, the spin texture of the Dirac states is also modified, which is described by introducing an effective Hamiltonian. Our findings not only are of fundamental interest but also have practical implications in potential applications of topological insulators.