Superconductivity up to 11.1 K in three solvated salts composed of [Ag (CF 3) 4] − and the organic electron-donor molecule bis (ethylenedithio) tetrathiafulvalene (ET)

Abstract

Electrocrystallization of the electron-donor molecule BEDT-TTF [bis (ethylenedithio) tetrathiafulvalene] with the square planar organometallic anion [Ag(CF 3) 4] − in TCE (1,1,2-trichloroethane) results in the formation of at least four crystalline phases. A plate-like phase, κ L-(ET) 2Ag(CF 3) 4· TCE, is isostructural to κ L-(ET) 2Cu(CF 3) 4· TCE T c = 4.0 K with a slightly expanded unit cell, but a lower critical temperature of 2.6 K. Two superconducting needle phases of (ET) 2Ag(CF 3) 4· TCE have been observed, with critical temperatures of 9.4 and 11.1 K. The critical temperature of this latter phase is within 0.5 K of the current record for ambient pressure organic superconductors, 11.6 K in κ-(ET) 2Cu[N(CN) 2]Br. A fourth phase, (ET) 2Ag(CF 3) 4, crystallizes simultaneously with the plates and needles, contains no solvent molecules, and does not superconduct down to 0.7 K.