First principles study on iron pnictide superconductor Ca _(0.88)Pr_(0.12)Fe_2As_2

摘要

The electronic structure, lattice dynamics, and electron-phonon (e-ph) coupling constant λ for the superconducting Ca_(0.88)Pr _(0.12)Fe_2As_2 are obtained by first principles calculations using norm-conserving pseudopotentials within virtual-crystal approximation treatment. The obtained λ for Ca_(0.88)Pr _(0.12)Fe_2As_2 is 0.45. Combined with the e-ph coupling constants λ for the superconducting CaFe_2As _(1.925)P_(0.075) and vicinity of collapsed tetragonal phase of CaFe_2As_2, we show that although the obtained λ for them cannot account for the high superconducting transition temperatures T C, they are a factor of two larger than that estimated in early calculations using the ultrasoft pseudopotentials for that of vicinity of collapsed tetragonal phase of CaFe_2As_2. We confirm that superconductivity in CaFe_2As_2 is not primarily phonon mediated. Nevertheless, the e-ph interactions are strong enough to be not negligible to investigate the superconductivity.