Spin-orbit interaction effect in the electronic structure of Bi ₂Te₃ observed by angle-resolved photoemission spectroscopy

The electronic structure of p-type doped Bi₂Te₃ is studied by angle-resolved photoemission spectroscopy (ARPES) to experimentally confirm the mechanism responsible for the high thermoelectric figure of merit. Our ARPES study shows that the band edges are located off the Γ-Z line in the Brillouin zone, which provides direct observation that the spin-orbit interaction is a key factor to understand the electronic structure and the corresponding thermoelectric properties of Bi₂Te₃. A successive time-dependent ARPES measurement also reveals that the electron-like bands crossing E_F near the -point are formed in an hour after cleaving the crystals. We interpret these as surface states induced by surface band bending, possibly due to quintuple inter-layer distance change of Bi ₂Te₃.