The characterization of organic charge transfer superconductors by microreflectance FTIR spectroscopy

This paper reports that certain classes of organic charge transfer salts exhibit superconducting behavior at liquid helium temperatures. These salts are typically prepared from a solution of ET (bis(ethylenedithio)tetrathiafulvene) and N(Bu)4X, where X is an anion; the salts form opaque crystallites 200 to 500 micrometers long on platinum electrodes. These salts may exist as the alpha, beta, or kappa phase, and their crystal structures have been determined by Williams and his co-workers (1,2) by X-ray diffraction. In the crystal structure, anion cavities exist between the radical cation stacks. Phase transitions between the various crystal forms occur when the salts are subjected to high pressure or when they are heated well above ambient temperature