Giant Interaction-Induced Gap and Electronic Phases in Rhombohedral Trilayer Graphene

TL;DR

This study reveals that rhombohedral trilayer graphene intrinsically exhibits a giant interaction-induced insulating gap due to spontaneous symmetry breaking, which can be controlled by various external parameters, offering potential for low-power electronic switches.

Contribution

The paper demonstrates that r-TLG is an intrinsic insulator with a large interaction-induced gap, contrary to theoretical predictions, and identifies its spontaneous antiferromagnetic nature and tunability.

Findings

r-TLG has a giant interaction-induced gap of ~42 meV.

The insulating state is a spontaneous layer antiferromagnet with broken time reversal symmetry.

The gap can be suppressed by increasing charge density, interlayer potential, magnetic field, or temperature.

Abstract

Due to their unique electron dispersion and lack of a Fermi surface, Coulomb interactions in undoped two-dimensional Dirac systems, such as single, bi- and tri-layer graphene, can be marginal or relevant. Relevant interactions can result in spontaneous symmetry breaking, which is responsible for a large class of physical phenomena ranging from mass generation in high energy physics to correlated states such as superconductivity and magnetism in condensed matter. Here, using transport measurements, we show that rhombohedral-stacked trilayer graphene (r-TLG) offers a simple, yet novel and tunable, platform for study of various phases with spontaneous or field-induced broken symmetries. Here, we show that, contrary to predictions by tight-binding calculations, rhombohedral-stacked trilayer graphene (r-TLG) is an intrinsic insulator, with a giant interaction-induced gap {\Delta}~42meV. This insulating state is a spontaneous layer antiferromagnetic with broken time reversal symmetry, and can be suppressed by increasing charge density n, an interlayer potential, a parallel magnetic field, or a critical temperature Tc~38K. This gapped collective state can be explored for switches with low input power and high on/off ratio.