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

We report the effect of Pt doping on the superconductivity in ${\mathrm{CuRh}}₂{\mathrm{Se}}₄$ spinel using a combined experimental and theoretical study. Our x-ray diffraction results reveal that the $\mathrm{Cu}{({\mathrm{Rh}}_{1\text{\ensuremath{-}}x}{\mathrm{Pt}}_x)}₂{\mathrm{Se}}₄ (0\ensuremath{\le}x\ensuremath{\le}0.35)$ crystallizes in the structure with a space group of $Fd\overline{3}m$ (No. 227), and the lattice parameter $a$ increases with Pt doping. The resistivity and magnetic susceptibility measurement results verify that the superconducting transition temperature (${T}_c$) 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 ${\mathrm{CuRh}}₂{\mathrm{Se}}₄$ to 168 Oe in $\mathrm{Cu}{({\mathrm{Rh}}_0.94{\mathrm{Pt}}_0.06)}₂{\mathrm{Se}}₄$, while it significantly enhances the upper critical magnetic field, reaching the maximum of 4.93 T in the $\mathrm{Cu}{({\mathrm{Rh}}_0.94{\mathrm{Pt}}_0.06)}₂{\mathrm{Se}}₄$ sample. The heat capacity result indicates that the sample $\mathrm{Cu}{({{\mathrm{Rh}}_0.}₉₁{{\mathrm{Pt}}_0.0}₉)}₂{\mathrm{Se}}₄$ 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 ${T}_{\mathrm{c}}$ observed experimentally.