Observation of an electrically tunable band gap in trilayer graphene

TL;DR

This paper demonstrates that ABC-stacked trilayer graphene can have its electronic band gap tuned by an electric field, unlike ABA-stacked trilayers, highlighting the importance of stacking order.

Contribution

It reveals that the stacking sequence in trilayer graphene critically influences the ability to induce a band gap with an electric field, a previously overlooked factor.

Findings

ABC stacking allows a large, tunable band gap under electric field.

Infrared conductivity confirms the presence of the band gap.

Stacking order determines the electronic properties of trilayer graphene.

Abstract

A striking feature of bilayer graphene is the induction of a significant band gap in the electronic states by the application of a perpendicular electric field. Thicker graphene layers are also highly attractive materials. The ability to produce a band gap in these systems is of great fundamental and practical interest. Both experimental and theoretical investigations of graphene trilayers with the typical ABA layer stacking have, however, revealed the lack of any appreciable induced gap. Here we contrast this behavior with that exhibited by graphene trilayers with ABC crystallographic stacking. The symmetry of this structure is similar to that of AB stacked graphene bilayers and, as shown by infrared conductivity measurements, permits a large band gap to be formed by an applied electric field. Our results demonstrate the critical and hitherto neglected role of the crystallographic stacking sequence on the induction of a band gap in few-layer graphene.