Gate Tunable Relativistic Mass and Berry$'$s phase in Topological Insulator Nanoribbon Field Effect Devices

TL;DR

This study demonstrates gate-tunable Dirac fermions and Berry's phase in topological insulator nanoribbons, revealing linear dispersion and surface state conduction through transport measurements, advancing topological device development.

Contribution

It provides direct transport evidence of gate-tunable Dirac fermions and Berry's phase in Bi2Te3 nanoribbons, showcasing control over topological surface states.

Findings

Observation of gate-tunable Berry's phase in oscillations

Detection of linear energy-momentum dispersion

Transition from weak anti-localization to localization

Abstract

Transport due to spin-helical massless Dirac fermion surface state is of paramount importance to realize various new physical phenomena in topological insulators, ranging from quantum anomalous Hall effect to Majorana fermions. However, one of the most important hallmarks of topological surface states, the Dirac linear band dispersion, has been difficult to reveal directly in transport measurements. Here we report experiments on Bi2Te3 nanoribbon ambipolar field effect devices on high-k SrTiO3 substrates, where we achieve a gate-tuned bulk metal-insulator transition and the topological transport regime with substantial surface state conduction. In this regime, we report two unambiguous transport evidences for gate-tunable Dirac fermions through {\pi} Berry$'$s phase in Shubnikov-de Haas oscillations and effective mass proportional to the Fermi momentum, indicating linear energy-momentum dispersion. We also measure a gate-tunable weak anti-localization (WAL) with 2 coherent conduction channels (indicating 2 decoupled surfaces) near the charge neutrality point, and a transition to weak localization (indicating a collapse of the Berry$'$s phase) when the Fermi energy approaches the bulk conduction band. The gate-tunable Dirac fermion topological surface states pave the way towards a variety of topological electronic devices.