  We introduce a dinstint approach to engineer a topologically protected
surface state of a topological insulator. By covering the surface of a
topological insulator, Bi2Te2Se, with a Bi monolayer film, the original surface
state is completely removed and three new spin helical surface states,
originating from the Bi film, emerge with different dispersion and spin
polarization, through a strong electron hybridization. These new states play
the role of topological surface states keeping the bulk topological nature
intact. This mechanism provides a way to create various different types of
topologically protected electron channels on top of a single topological
insulator, possibly with tailored properties for various applications.
