  By using angle-resolved photoemission spectroscopy combined with
first-principles calculations, we reveal that the topmost unit cell of ZrSnTe
crystal hosts two-dimensional (2D) electronic bands of topological insulator
(TI) state, though such a TI state is defined with a curved Fermi level instead
of a global band gap. Furthermore, we find that by modifying the dangling bonds
on the surface through hydrogenation, this 2D band structure can be manipulated
so that the expected global energy gap is most likely to be realized. This
facilitates the practical applications of 2D TI in heterostructural devices and
those with surface decoration and coverage. Since ZrSnTe belongs to a large
family of compounds having the similar crystal and band structures, our
findings shed light on identifying more 2D TI candidates and superconductor-TI
heterojunctions supporting topological superconductors.
