Pressure-induced insulator-to-metal transition and superconductivity in iodanil, C 6I 4O 2

Abstract

Electrical properties of iodanil (C 6I 4O 2) have been studied at low temperatures and at very high pressures. An insulator-to-metal transition in this compound is found at about 30 GPa. Further, iodanil shows superconductivity at about 2 K above 52 GPa. The magnetic field dependence of the transition temperature was measured at low temperatures under 78 GPa. The superconductivity of iodanil is suppressed by an applied magnetic field. This is the first observation of superconductivity in simple organic molecular crystals. The electronic spectra of a thin film of iodanil were measured up to 30 GPa at room temperature. The absorption intensity in the near infrared region increases markedly with increasing pressure above 16 GPa. This optical behavior is closely related to the insulator-metal transition at about 30 GPa. The insulator–metal transition and the superconductivity of iodanil at very high pressures are discussed.