Observation of Dirac Holes and Electrons in a Topological Insulator

TL;DR

This study demonstrates surface-dominated transport in a topological insulator, revealing the coexistence of Dirac holes and electrons on the surface, and tracks their evolution over time.

Contribution

It reports the first observation of both Dirac holes and electrons on the surface of a topological insulator and links their dynamics to surface chemical potential changes.

Findings

Surface channel contributes up to 70% of conductance.

Sign change in Hall coefficient over time.

Observation of both Dirac holes and electrons.

Abstract

We show that in the new topological-insulator compound Bi_{1.5}Sb_{0.5}Te_{1.7}Se_{1.3} one can achieve a surfaced-dominated transport where the surface channel contributes up to 70% of the total conductance. Furthermore, it was found that in this material the transport properties sharply reflect the time dependence of the surface chemical potential, presenting a sign change in the Hall coefficient with time. We demonstrate that such an evolution makes us observe both Dirac holes and electrons on the surface, which allows us to reconstruct the surface band dispersion across the Dirac point.