FERMI SURFACES OF ORGANIC SUPERCONDUCTORS

In this review an overview of the present-day knowledge of the Fermi surfaces of organic superconductors obtained by Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) experiments is given. Almost all measurements reported here were made on charge transfer salts of the type (ET)2X where ET stands for bis(ethelenedithio)-tetrathiafulvalene (or BEDT-TTF) and X is a monovalent anion. The ET-salts are characterized by their extremely two-dimensional properties. Some unique features resulting from this two-dimensionality, like gigantic SdH and dHvA oscillations, directly observable spin-splitting far from the quantum limit and a distinctive angular dependence of the dHvA amplitude will be discussed in detail. By comparison of the measured cyclotron effective mass with the bare band mass the electron-phonon coupling constant can be extracted and the validity of the BCS formula for the superconducting transition temperature can be checked.

THE FLUORINE RESONANCE SPECTRUM OF PERCHLORYL FLUORIDE

The first instance of observable spin–spin coupling with a chlorine nucleus is found in the fluorine resonance of perchloryl fluoride. The explanations of this, and of the very large chemical shift, are given.