Ambipolar Electric Field Effect in Metallic Bi2Se3

TL;DR

This paper demonstrates electric field control of surface state density in metallic Bi2Se3 nanoscale devices, enabling ambipolar transport and advancing the integration of topological insulators into electronic applications.

Contribution

It introduces a method to electrically tune the surface states of Bi2Se3 using high-k dielectrics, overcoming bulk doping issues for device integration.

Findings

Fermi energy can be shifted through the charge neutrality point.

Ambipolar transport characteristics similar to graphene are observed.

Surface state mobility and scattering mechanisms are characterized.

Abstract

Topological insulators (TIs) constitute a new class of materials with unique properties resulting from the relativistic-like character and topological protection of their surface states. Theory predicts these to exhibit a rich variety of physical phenomena such as anomalous magneto-electric coupling and Majorana excitations. Although TI surface states have been detected in Bi-based compounds by ARPES and STM techniques, electrical control over their density, required for most transport experiments, remains a challenge. Existing materials are heavily doped in the bulk, thus preventing electrical tunability of the surface states and their integration into topological quantum electronic devices. Here we show that electronic transport in metallic Bi2Se3 nanoscale devices can be controlled by tuning the surface density via the electric field effect. By choosing an appropriate high-k dielectric, we are able to shift the Fermi energy through the charge neutrality point of the surface states, resulting in ambipolar transport characteristics reminiscent of those observed in graphene. Combining magnetotransport, field effect, and geometry dependent experiments, we provide transport measurements of the surface state mobility, and identify likely scattering mechanisms by measuring its temperature dependence.