Organic layered superconductors

Abstract The recent experimental data on the normal and superconducting properties of organic compounds β-(ET)2X in comparison with (TMTSF)2X are analysed. Special attention is paid to the structural pecularities of these crystals, electron band structure, T 2 law of resistivity, the superconducting properties near T c and at low temperatures and the effect of disorder on T c. It is argued that the term T 2 in the resistivity arises from the Coulomb interaction of electrons. The BCS model gives a satisfactory description of superconductivity near T c but it seems to fail in the region T ≪ T c in high-T c compounds such as βH-(ET)2I3 and β-(ET)2AuI2. The experimental data on the temperature dependence of the upper critical field and the superconducting gap in these compounds provide evidence in favour of an extremely strong coupling model.

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