Heavy boron doping in superconducting carbon materials

We examine physical properties of heavily boron-doped $s{p}^{3}$-hybridized carbon allotropes: cubic diamond, hexagonal diamond, and body centered tetragonal ${\mathrm{C}}_{4}$. The structural similarity between cubic diamond and hexagonal diamond leads to similar responses to substitutional boron doping. On the other hand, body centered tetragonal ${\mathrm{C}}_{4}$ exhibits distinct structural and electronic properties because of its characteristic structure. Our study also shows that the superconducting transition temperatures up to 60 K are possible in heavily doped carbon materials despite their various atomistic structures.