Origin of Superconductivity in Boron-doped Diamond

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Superconductivity of boron-doped diamond, reported recently at Tc=4 K, is investigated exploiting its electronic and vibrational analogies to MgB2. The deformation potential of the hole states arising from the C-C bond stretch mode is 60% larger than the corresponding quantity in MgB2 that drives its high Tc, leading to very large electron-phonon matrix elements. The calculated coupling strength λ 0.5 leads to Tc in the 5-10 K range and makes phonon coupling the likely mechanism. Higher doping should increase Tc somewhat, but effects of three dimensionality primarily on the density of states keep doped diamond from having a Tc closer to that of MgB2.