Scaling Approach to Electronic Correlations in Organic Conductors

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The problem of electronic correlations in organic conductors like the Bechgaard salt series [(TMTSF)2X] is well known to be at the heart of the remarkable richness of phase transitions observed in these materials [1], The well established quasi-one-dimensionality of these materials makes both the phenomenological and the microscopic descriptions of correlations rather delicate. Correlations are actually characterized by various energy scales. This is mainly imposed for example by strongly anisotropic hopping integrals for the electrons and the sizeable on-chain Coulomb repulsion. The scaling hypothesis [3] and its extended version [3b] for the inclusion of crossover effects between various energy scales then appears as a natural description of correlations in these materials [2]. The microscopic calculations must in turn confirm that this ansatz actually holds. Here, we give a brief survey of the applicability of the scaling hypothesis for the description of itinerant antiferromagnetism in the Bechgaard salts. We will focuss our attention on the recent NMR relaxation rate and EPR line width data. These two observable quantities are directly coupled to magnetic fluctuations and scaling allows a remarkable clarification of several aspects of correlations. Dimensionality and the respective weight associated to uniform and antiferromagnetic correlations are analyzed as function temperature and hydrostatic pressure.