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

TL;DR

This paper reports the discovery of superconductivity in Cu(Ir1-xPtx)2Se4 spinel, with optimal Tc at x=0.2, and explores its electronic structure, superconducting properties, and comparison to related compounds.

Contribution

It introduces superconductivity in Cu(Ir1-xPtx)2Se4 spinel and analyzes its electronic structure, critical field, and relation to charge order, highlighting the role of spin orbit coupling.

Findings

Superconductivity observed at Tc = 1.76 K for x=0.2.

Superconducting state is BCS-like with a high upper critical field.

Superconductivity not necessarily linked to charge order destabilization.

Abstract

We report the observation of superconductivity in the CuIr2Se4 spinel induced by partial substitution of Pt for Ir. The optimal doping level for superconductivity in Cu(Ir1-xPtx)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 {\Delta}C/{\gamma}Tc, 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 (mu0Hp), 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.