Rb-intercalated bilayer graphene studied by high-resolution ARPES

To elucidate the electronic structure at the thinnest limit of the graphite intercalation compound (GIC) C$_8$Rb, we have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED) on Rb-intercalated bilayer graphene fabricated by in-situ evaporation of Rb atoms onto graphene grown epitaxially on SiC. Using LEED, the creation of an intercalated layer with in-plane geometry identical to bulk GICs was confirmed by the observation of a 2x2 spot pattern consistent with Rb intercalation. From ARPES measurement, we found that the Dirac point is at a binding energy of approximately 1 eV, compared to 0.4 eV in pristine epitaxial graphene on SiC [1]. The Fermi surface of this material was also measured. The critical differences between C$_8$Rb, its sister compound C$_8$K, and pristine bilayer graphene will be examined herein.\\[4pt] [1] T. Ohta et al, Science 313, 951-4 (2006).