Superconductivity in the Cu(Ir1-xPtx)2Se4 spinel

Abstract

We report the observation of superconductivity in the CuIr 2Se4 spinel induced by partial substitution of Pt for Ir. The optimal doping level for superconductivity in Cu(Ir1-xPt x)2Se4 is x = 0.2, where Tc is 1.76 K. A superconducting Tc vs composition dome is established between the metallic, normal conductor CuIr2Se4 and semiconducting CuIrPtSe4. Electronic structure calculations show that the optimal Tc occurs near the electron count of a large peak in the calculated electronic density of states and that CuIrPtSe4 is a band-filled insulator. Characterization of the superconducting state in this heavy metal spinel through determination of ΔC/γTc indicates that it is BCS-like. The relatively high upper critical field at the optimal superconducting composition [Hc2(0) = 3.2 T] is much larger than that reported for analogous rhodium spinels and is comparable to or exceeds the Pauli field (μ0HP), suggesting that strong spin-orbit coupling may influence the superconducting state. Further, comparison to doped CuIr2S4 suggests that superconductivity in iridium spinels is not necessarily associated with the destabilization of a charge-ordered spin-paired state through doping. © 2013 American Physical Society.