Charge-density wave in Ca-intercalated bilayer graphene induced by commensurate lattice matching

We report the emergence of a charge-density wave (CDW) in Ca-intercalated bilayer graphene (C_{6}CaC_{6}), the thinnest limit of superconducting C_{6}Ca, observed by low-temperature, high-magnetic-field scanning tunneling microscopy or spectroscopy, and angle-resolved photoemission spectroscopy. While the possible superconductivity was not observed in epitaxially grown C_{6}CaC_{6} on a SiC substrate, a CDW order different from that observed on the surface of bulk C_{6}Ca was observed. It is inferred that the CDW state is induced by the potential modulation due to the commensurate lattice matching between the C_{6}CaC_{6} film and the SiC substrate.