We present a systematical study on the roles of interactions among electron correlation, electron-phonon coupling, and spin-orbit coupling in the isovalent Pd-substituted superconductor ${\mathrm{SrPt}}_3\mathrm{P}$. By using the solid state reaction method, the Pd element with the $4d$ orbital was successfully substituted in the strong spin-orbit coupling superconductors $\mathrm{Sr}{\left({\mathrm{Pt}}_{1-x}{\mathrm{Pd}}_x\right)}_3\mathrm{P}$. As increasing the isovalent Pd concentrations without introducing any extra electron/hole carriers, the superconducting transition temperature $T_c$ decreases monotonously. In addition, combining the data of resistivity and specific heat, as well as electronic band structure calculations, we found that the electron correlation is enhanced while the electron-phonon coupling and the spin-orbit coupling are suppressed by Pd substitution. Our results may provide significant insights in the natures of the interplay among the electron correlation, electron-phonon coupling, and spin-orbit coupling in superconductivity, and may also pave a route for understanding the mechanism of superconductivity in heavily $5d$-based superconductors.

• Received 10 January 2016
• Revised 16 May 2016

DOI:https://doi.org/10.1103/PhysRevB.93.214510