Observation of Huge Surface Hole Mobility in the Topological Insulator Bi0.91Sb0:09 (111)

We report the first direct measurement of transport properties of surface states in the topological insulator Bi0.91Sb0.09 (111) from the weak-field Hall effect and Shubnikov-de Haas oscillations. We find that the holelike surface band displays an unexpectedly high mobility 23 000-85 000 cm(2)/Vs, which is the highest mobility so far reported in bismuth-based topological insulators. This result provides the first quantitative assessment of the effect of alloy disorder on the mobility of surface states in topological insulators. We show that the 9% alloy disorder decreases the mobility of surface states by a factor of less than 2.3.