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

TL;DR

This paper provides experimental evidence of topological surface states in beta-Ag2Te nanoplates, demonstrating their large electric tunability, high mobility, and quantum oscillations indicative of topological insulator behavior.

Contribution

It reports the first observation of gate-tuned quantum oscillations and a near pi Berry phase in beta-Ag2Te, establishing it as a promising topological insulator with high tunability.

Findings

Observation of 2D Shubnikov-de Haas oscillations.

Large electric field ambipolar effect (~2500%).

High mobility (~3x10^4 cm^2s^-1V^-1) near the Dirac point.

Abstract

We report the strong experimental evidence of the existence of topological surface states with large electric field tunability and mobility in beta-Ag2Te. Pronounced 2D SdH oscillations have been observed in beta-Ag2Te nanoplates. A Berry phase is determined to be near pi using the Landau level fan diagram for a relatively wide nanoplate while the largest electric field ambipolar effect in topological insulator so far (~ 2500%) in a narrow nanoplate. The pi Berry phase and the evolution of quantum oscillations with gate voltage (Vg) in the nanoplates strongly indicate the presence of topological surface states in beta-Ag2Te. Moreover, the mobility of the narrow Ag2Te nanoplate is ~ 3x10^4 cm^2s^-1V^-1 when the Fermi level is near the Dirac point. The realization of topological surface states with large electrical tunability and high mobility indicates that beta-Ag2Te is a promising topological insulator for fundamental studies.