Edge engineering of a topological Bi(111) bilayer

Our first-principles simulations demonstrate the precise engineering of edge states by chemical decoration in topological Bi(111) bilayer nanoribbons. The chemical passivation removes the trivial edge states, recovers the Dirac linear dispersion of the topological edge state, and significantly influences both transport and optical signatures. Our transport simulations show that the Bi(111) bilayer nanoribbon offers an ideal system for assessing conductance fluctuation of edge states of a quantum spin Hall system by comparing the edge state transport with and without chemical decoration. The spatial extent and spin texture of edge states also become engineerable with the chemical decoration.