Flat Electronic Bands in Long Sequences of Rhombohedral-stacked Multilayer Graphene

TL;DR

This study directly images flat electronic bands in large rhombohedral-stacked multilayer graphene, revealing potential for correlated electronic phenomena such as superconductivity and magnetism.

Contribution

It provides the first experimental visualization of flat bands in large ABC-stacked multilayer graphene using angle-resolved photoemission spectroscopy.

Findings

Flat bands extend by 0.13 Å^{-1} at the Fermi level near the K point.

First-principle calculations show an antiferromagnetic ground state with a 40 meV band gap.

Experimental data supports the presence of correlated electronic states.

Abstract

The crystallographic stacking order in multilayer graphene plays an important role in determining its electronic properties. It has been predicted that a rhombohedral (ABC) stacking displays a conducting surface state with flat electronic dispersion. In such a flat band, the role of electron-electron correlation is enhanced possibly resulting in high Tc superconductivity, charge density wave or magnetic orders. Clean experimental band structure measurements of ABC stacked specimens are missing because the samples are usually too small in size. Here, we directly image the band structure of large multilayer graphene flake containing approximately 14 consecutive ABC layers. Angle-resolved photoemission spectroscopy experiments reveal the flat electronic bands near the K point extends by 0.13 {\AA}-1 at the Fermi level at liquid nitrogen temperature. First-principle calculations identify the electronic ground state as an antiferromagnetic state with a band gap of about 40 meV.