Quantum transport of two-species Dirac fermions in dual-gated three-dimensional topological insulators

TL;DR

This paper investigates the quantum transport properties of two-species Dirac fermions on the surfaces of dual-gated three-dimensional topological insulators, revealing novel quantum phenomena and tunable electronic states.

Contribution

It demonstrates independent control of top and bottom surface Dirac fermions in a topological insulator, uncovering new quantum Hall states and transport behaviors.

Findings

Observation of a zero-magnetic-field minimum conductivity near twice the conductance quantum.

Identification of ambipolar two-component half-integer Dirac quantum Hall states.

Detection of an electron-hole total filling factor zero state with a zero-Hall plateau.

Abstract

Topological insulators are a novel class of quantum matter with a gapped insulating bulk yet gapless spin helical Dirac fermion conducting surface states. Here, we report local and non-local electrical and magneto transport measurements in dual-gated BiSbTeSe2 thin film topological insulator devices, with conduction dominated by the spatially separated top and bottom surfaces, each hosting a single species of Dirac fermions with independent gate control over the carrier type and density. We observe many intriguing quantum transport phenomena in such a fully-tunable two-species topological Dirac gas, including a zero-magnetic-field minimum conductivity close to twice the conducatance quantum at the double Dirac point, a series of ambipolar two-component half-integer Dirac quantum Hall states and an electron-hole total filling factor zero state (with a zero-Hall plateau), exhibiting dissipationless (chiral) and dissipative (non-chiral) edge conduction respectively. Such a system paves the way to explore rich physics ranging from topological magnetoelectric effects to exciton condensation.