Superconductors (SCs) are attractive materials in all respects for any community. They provide a deep insight into the physical properties of the condensed matters and also have useful applications as ultra-low-power-dissipation systems that can help resolve the present energy problems. In particular, the recent advancement of carbon-based new superconductors (CNSCs) is significant. Before 2004, the superconducting transition temperature (Tc) of carbon-based SCs was below 1 K, except in fullerene clusters. However, in 2004, a Russian group discovered that diamond highly doped with boron could be an SC at Tc = 4 K. The following year, a group from Cambridge found that calcium-intercalated graphite could be an SC with Tc = 11.5 K. In 2006 and 2008, the editor’s group from Japan also discovered that carbon nanotubes could be SCs at Tc = 12 K. Since then, research on CNSCs has increased notably.
A small mass of carbon can produce high phonon frequency and high Debye temperature. Combining these with other specified properties of CNSCs (such as one-dimensional electronic states) is highly expected to open doors to high-Tc superconductivity like those of CuO₂- and Fe-based SCs, which were the only SCs to show Tc > 40 K in the past. CNSCs, such as diamond, graphite, carbon nanotubes, fullerenes, and others, are a very attractive field of research, and this book is the first to describe their basic physics and the recent advances toward high Tc in this field.