Theoretical investigation of superconductivity in diamond: Effects of doping and pressure

摘要

The electronic structure, lattice dynamics, and electron-phonon coupling of pure, boron and nitrogen-doped diamond carbon were investigated using first-principle calculations within the generalized-gradient and virtual crystal approximations. To examine the influence of the impurity content and pressure on the superconductivity of these systems, the electron-phonon coupling constant (λ) and the critical temperature (T_c) were calculated as a function of concentrations from 0 to 15% and pressures from 0 to 90 GPa. Regarding the boron-doped diamond, calculations indicated that its electron-phonon coupling strongly relates to the optical phonon modes, and the estimated critical temperatures matched previous theoretical and experimental results. Regarding the nitrogen-doped case, it was observed that both λ and T_c were larger than those obtained for the hole-doped case. The most distinguishing feature of this system was its rising acoustic contribution to the electron-phonon coupling, which led to significant values for λ and T_c. The majority of the scenarios investigated here presented a decreasing critical temperature with increasing pressure. In contrast to the other cases, C_(0.85)N_(0.15) exhibited a positive dependence between T_c and pressure leading to a superconducting transition temperature of about 122 K at 20 GPa.