Direct Probing Stacking Order and Electronic Spectrum of Rhombohedral   Trilayer Graphene with Scanning Tunneling Microscopy
  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. 
Rui Xu, Long-Jing Yin, Jia-Bin Qiao, Ke-Ke Bai, Jia-Cai Nie, and Lin   He
cond-mat.mes-hall cond-mat.mtrl-sci