Pressure-Induced 18 K Superconductivity and Two Superconducting Phases in CuIr2S4

Abstract

We report pressure-induced superconductivity in the spinel CuIr2S4 with a transition temperature (Tc) reaching 18.2 K, establishing a new record for this class of materials and surpassing the decades-old limit of 13.7 K. Our electrical transport and synchrotron x-ray diffraction studies up to 224 GPa reveal the emergence of two distinct superconducting phases from a charge-ordered insulating state. The first phase (SC-I) appears around 18 GPa, and forms a dome-shaped superconducting region in which the resistivity exhibits a pronounced, field- and current-sensitive drop without reaching strict zero above our base temperature. Above 111.8 GPa, a second, lower-Tc phase (SC-II) emerges and coexists with SC-I over a broad pressure range, and SC-II ultimately develops a true zero-resistance state above 122.2 GPa. These superconducting phases are intimately linked to a cascade of structural transitions that systematically distort the frustrated pyrochlore lattice of Ir atoms. Our results expand the potential for superconductivity in spinels and demonstrate a pathway to high-Tc pairing directly from a correlated insulating state driven by lattice tuning.

Source-reported materials — not catalogue approval

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