PROBLEM TO BE SOLVED: To obtain a superconducting substance showing superconductive characteristics by the doping with a carrier by elemental substitution and exhibiting characteristics common to a copper oxide superconducting substance by using a superconducting sulfide spinel substance having a specific composition composed of Cu, Zn, Ir and S.
SOLUTION: The objective substance has a composition formula of Cu1-xZnxIr2S4 (0.25≤x≤0.8). CuIr2S4 is a sulfide spinel substance exhibiting a metal-insulator transition at about 230K and is a metal at the high-temperature side and an insulator at the low-temperature side. The Cu is univalent at the low-temperature side. The substance of the above composition formula obtained by substituting the univalent Cu with bivalent Zn has superconductive transition and gives a superconductive characteristic showing Meissner effect at the superconductive transition temperature. The superconductive character of the substance is developed by the doping of carrier by elemental substitution. The substance is converted to superconducting state from a state having a resistance about five orders in magnitude larger than the resistance of the superconducting state and the state is lost by a small pressure change of ≤100 bar.