A Single-Component Molecular Superconductor

The pressure dependence of the resistivities of a single-component molecular conductor, [Ni(hfdt)(2)] (hfdt = bis(trifluoromethyl)tetrathiafulvalenedithiolate) with semiconducting properties at ambient pressure was examined. The four-probe resistivity measurements were performed up to similar to 10 GPa using a diamond anvil cell. The low-temperature insulating phase was suppressed above 7.5 GPa and the resistivity dropped, indicating the superconducting transition occurred around 7.5-8.7 GPa with a maximum T-c(onset temperature) of 5.5 K. The high-pressure crystal and electronic band structures were derived by the first-principle calculations at 6-11 GPa. The crystal was found to retain the semiconducting band structure up to 6 GPa. But the electron and hole Fermi surfaces appear at 8 GPa. These results of the calculations agree well with the observation that the pressure-induced superconducting phase of [Ni(hfdt)(2)] appeared just above the critical pressure where the low-temperature insulating phase was suppressed.