Research groups of the University of Tokyo - Graduate School of Science, Waseda University - School of Science and Technology, JAEA - Advanced Science Research Center, and KEK - Institute for Materials Structure Science determined the atomic structure of superconducting Ca-intercalated bilayer graphene on a SiC (0001) substrate using total-reflection high-energy positron diffraction (TRHEPD).By comparing the experimental rocking-curves with ones calculated for various structural models using a full-dynamical theory, it has been found that Ca atoms are intercalated in the graphene-buffer interlayer, rather than between the two graphene layers. From transport measurements, the superconducting transition was observed to be at Tconset = 4 K for this structure. This study is the first to clearly identify the relation between the atomic arrangement and superconductivity in Ca-intercalated bilayer graphene.
Carbon 157, 857-862 (2020) (Available online 25 October 2019).
