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Ca intercalated bilayer graphene as a thinnest limit of superconducting C₆Ca

Kanetani, Kohei, Sugawara, Katsuaki, Sato, Takafumi, Shimizu, Ryota, Iwaya, Katsuya, Hitosugi, Taro, Takahashi, Takashi
Proceedings of the National Academy of Sciences of the United States of America 2012 v.109 no.48 pp. 19610-19613
graphene, physical properties, scanning tunneling microscopy, silicon carbide, spectroscopy
Success in isolating a 2D graphene sheet from bulky graphite has triggered intensive studies of its physical properties as well as its application in devices. Graphite intercalation compounds (GICs) have provided a platform of exotic quantum phenomena such as superconductivity, but it is unclear whether such intercalation is feasible in the thinnest 2D limit (i.e., bilayer graphene). Here we report a unique experimental realization of 2D GIC, by fabricating calcium-intercalated bilayer graphene C ₆CaC ₆ on silicon carbide. We have investigated the structure and electronic states by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. We observed a free-electron–like interlayer band at the Brillouin-zone center, which is thought to be responsible for the superconductivity in 3D GICs, in addition to a large π* Fermi surface at the zone boundary. The present success in fabricating Ca-intercalated bilayer graphene would open a promising route to search for other 2D superconductors as well as to explore its application in devices.