Gate-tuned quantum oscillations of topological surface states in β-Ag2Te

Abstract

We report the strong experimental evidence of the existence of topological surface states with large electric field tunability and mobility in β-Ag 2 Te. Pronounced 2D Shubnikov-de Haas oscillations have been observed in β-Ag 2 Te nanoplates. A Berry phase is determined to be near π using the Landau level fan diagram for a relatively wide nanoplate while the largest electric field ambipolar effect in topological insulator so far (∼2500%) is observed in a narrow nanoplate. The π Berry phase and the evolution of quantum oscillations with gate voltage (Vg) in the nanoplates strongly indicate the presence of topological surface states in β-Ag 2 Te. Moreover, the mobility of the narrow Ag 2 Te nanoplate is about several thousand cm2s-1V-1. Our results suggest that β-Ag2 Te has the potential to become an important material in the investigation of topological insulators.