Superconductivity with the enhanced upper critical field in the Pt-doped CuRh2Se4 spinel

We report the effect of Pt doping on the superconductivity in CuRh2Se4 spinel using a combined experimental and theoretical study. Our x-ray diffraction results reveal that the Cu(Rh1-xPtx)2Se4 (0 x 0.35) crystallizes in the structure with a space group of Fd 3 over bar m (No. 227), and the lattice parameter a increases with Pt doping. The resistivity and magnetic susceptibility measurement results verify that the superconducting transition temperature (Tc) forms a domelike shape with a maximum value of 3.84 K at x = 0.06. It is also observed that the Pt doping slightly reduces the lower critical magnetic field from 220 Oe in CuRh2Se4 to 168 Oe in Cu(Rh0.94Pt0.06)2Se4, while it significantly enhances the upper critical magnetic field, reaching the maximum of 4.93 T in the Cu(Rh0.94Pt0.06)2Se4 sample. The heat capacity result indicates that the sample Cu(Rh0.91Pt0.09)2Se4 is a bulk superconductor. First-principles calculations suggest that the Pt doping leads to a redshift of a density of state peak near the Fermi level, consistent with the domelike Tc observed experimentally.