Strong surface scattering in ultrahigh mobility Bi2Se3 topological insulator crystals

havebeen studied. A comprehensive analysis of Shubnikov de Haas oscillations, Hall effect, and opticalreflectivity indicates that the measured electrical transport can be attributed solely to bulk states,even at 50 mK at low Landau level filling factor, and in the quantum limit. The absence of asignificant surface contribution to bulk conduction demonstrates that even in very clean samples,the surface mobility is lower than that of the bulk, despite its topological protection.