Abstract
Low dimensional organic conductors exhibit a wide variety of physical properties which is exemplified by the observation of ground states such as Peierls, spin-Peierls, SDW and Superconducting states. We survey the experimental situation with a special emphasis on the family of the one-chain conductors to which the famous (TMTCF)2X series C = S, Se belongs.
Although the band picture seems to be a reasonable starting point for the understanding of these materials, interactions such as electron-phonon and electron-electron as well as the amplitude of the Umklapp scattering term and the size of the interchain tunneling coupling must all be taken into account. The amplitude of electron-electron interactions can be derived from a detailed analysis of the temperature dependence of the nuclear spin-lattice relaxation rate data. Coulomb interactions of the order of the bandwidth are found.
The interplay between magnetism and superconductivity is governed by the interchain overlap which can be varied under pressure. The possibility of a pairing mechanism based on the interchain exchange of 2kF spin fluctuations is strongly supported by experiments. In addition, a wealth of experimental features suggest the coexistence in the precursor (1-D) regime above long range ordering (magnetic or superconducting) of fluctuations simultaneously magnetic and superconducting.
The very fast increase of Tc for organic superconductors which has been observed in the last eight years is very stimulating for the future development of this field.
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