Direct Probing Stacking Order and Electronic Spectrum of Rhombohedral Trilayer Graphene with Scanning Tunneling Microscopy

TL;DR

This study uses scanning tunneling microscopy to directly probe the stacking order and electronic spectrum of rhombohedral trilayer graphene, revealing detailed energy gaps and flat band features linked to strongly correlated phenomena.

Contribution

It demonstrates a method to directly measure the stacking order and electronic spectrum of r-TLG using STM, providing detailed insights into its low-energy flat bands.

Findings

Identification of four adjacent peaks in tunneling spectra due to flat bands

Determination of the energy gap (~9 meV) and K-point gap (~23 meV)

Spectra well reproduced by a low-energy effective Hamiltonian

Abstract

Recently, the rhombohedral trilayer graphene (r-TLG) has attracted much attention because of its low-energy flat bands, which are predicted to result in many strongly correlated phenomena. Here, we demonstrate that it is possible to probe the stacking order and electronic spectrum of the r-TLG directly with a scanning tunneling microscopy around a monoatomic step edge of the top graphene layer. The tunneling spectra of the r-TLG exhibit four adjacent peaks, which are generated by the low-energy flat bands, flanking the charge neutrality point. Based on these spectra, the true energy gap and the energy gap at the K-point of the r-TLG are determined as about 9 meV and 23 meV, respectively. The observed features are well reproduced by a low-energy effective Hamiltonian.