Narrow Pressure Domain for Superconductivity in (TMTSEF) 2 ClO 4

Abstract
We present resistivity data for (TMTSeF)2C1O4 as a function of pressure. We find that the superconducting transition temperature (Tc) drops rapidly as pressure is increased from 1 bar (Tc≃1.3 K in slowly cooled samples) to below 50 mK above 4-5 kbar. This is a very rapid rate of decrease as compared to typical inorganic materials and is about three times that observed in the isostructural PF6 salt. In addition we find evidence that the second order transition near 24 K at 1 bar associated with ordering of the C1O4 anions is not significantly affected by pressure. We clearly observe this transition at about the same temperature for pressures up to 10 kbar.
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