Origin of Superconductivity in Boron-doped Diamond

TL;DR

This paper investigates the origin of superconductivity in boron-doped diamond, suggesting that strong electron-phonon coupling driven by bond stretch modes is responsible for its superconducting properties.

Contribution

It provides a theoretical analysis linking boron-doped diamond's superconductivity to electron-phonon interactions similar to MgB2, highlighting the role of deformation potential and coupling strength.

Findings

Deformation potential in boron-doped diamond is 60% larger than in MgB2.

Calculated electron-phonon coupling strength bb d 0.5 predicts T_c in 5-10 K range.

Phonon coupling is identified as the likely mechanism for superconductivity.

Abstract

Superconductivity of boron-doped diamond, reported recently at T_c=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 \lambda ~ 0.5 leads to T_c in the 5-10 K range and makes phonon coupling the likely mechanism. Higher doping should increase T_c somewhat, but effects of three dimensionality primarily on the density of states keep doped diamond from having a T_c closer to that of MgB2.