title: Strong coupling superconductivity at 8.4 K in an antiperovskite phosphide SrPt3P.
abstract: We report the discovery of a family of ternary platinum phosphides APt3P (A = Ca, Sr, and La), which crystallize in an antiperovskite-based structure closely related to that of the heavy fermion superconductor CePt3Si. All three phosphides showed superconductivity at low temperatures and the highest critical temperature T(c) = 8.4  K was observed for SrPt3P. The analysis of specific heat C(T) for SrPt3P shows clear evidence for very strong coupling s-wave superconductivity with a large ratio between superconducting gap Δ0 and T(c), 2Δ0/k(B)T(c) ∼ 5, and the presence of low-energy phonons. The presence of multiple Fermi surface pockets was inferred from the nonlinear magnetic field dependence of Hall resistivity, which we argue might play a role in realizing the strong coupling of charge carriers with the low-lying phonons.
authors.affiliation: Department of Advanced Materials, University of Tokyo, and JST-TRIP, Kashiwa, Chiba 275-8651, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takayama
authors.forename: K
authors.initials: K
authors.lastname: Kuwano
authors.forename: D
authors.initials: D
authors.lastname: Hirai
authors.forename: Y
authors.initials: Y
authors.lastname: Katsura
authors.forename: A
authors.initials: A
authors.lastname: Yamamoto
authors.forename: H
authors.initials: H
authors.lastname: Takagi