Competition Between Sdw and Superconductivity in (TMTSF)2X Compounds

Abstract

The phase diagram of a quasi-one-dimensional metal with retarded and nonretarded forward and backward scattering is derived. It is shown that singly charged acceptor molecules produce a potential along the conducting chains which leads to umklapp scattering. This umklapp scattering depends strongly on the phonon frequency and can explain the crossover from spin density waves to superconductivity as observed in the (TMTSF)₂X compounds. The relevance of recent magnetoresistance measurements to the proposed model is discussed. We have shown that the discovery of the (TMTSF)₂X Compounds requires some modifications in the “g-ology” picture which accompanied the field of one-dimensional metals since the beginning. In particular, the inclusion of retardation effects and umklapp scattering seems to be essential. When these are included, a simple and natural description of the behaviour of the (TMTSF)₂X compounds is obtained.