Superconducting and magnetic phases in quenched perchlorate Bechgaard salts

(TMTSF)2ClO4 is a quasi-1D organic conductor, in which the non-centrosymetric anion ClO4 undergoes an orientational order at 24 K. Structural studies have shown that in (TMTSF)2ClO4, samples cooled down through the anion ordering transition at 24 K, a certain amount of disorder is quenched: there appear, in the low T state, domains in which the anions are orientationaly ordered and domains in which they are disordered, with concentrations and sizes can be varied by varying the cooling rate. Such a structure is essential for the stability of the various phases which can appear. Here, the relevant parameter is not the mean anion potential, but the real values of the anion potential within each domain. When the sizes of the domains are larger than the coherence lengths, a functional renormalization group analysis shows that a d-wave superconducting order is more stable in the ordered domains, because of the gap opened on the Fermi surface by the periodic anion potential, while in the disordered domains, a SDW order is the stable one. There is a large range of cooling rates, in which these two kinds of domains coexist. In that case, in the low T state, a superconducting order and a SDW order exist together. These phases do not really coexist, but are indeed spatially segregated. When the sizes of the disordered domains are much smaller than the superconducting coherence length, they behave as non-magnetic impurities in the superconducting phase, which decrease the superconducting critical temperature, according to the Abrikosov–Gorkov law. Our results are in good agreement with recent experimental.