Europhys. Lett.
Volume 72, Number 4, November 2005
Page(s) 645 - 651
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 14 October 2005
Europhys. Lett., 72 (4), pp. 645-651 (2005)
DOI: 10.1209/epl/i2005-10281-1

Impurity-controlled superconductivity/spin density wave interplay in the organic superconductor: $\chem{(TMTSF)_2ClO_4}$

N. Joo1, 2, P. Auban-Senzier1, C. R. Pasquier1, D. Jérome1 and K. Bechgaard3

1  Laboratoire de Physique des Solides (UMR 8502) - Université Paris-Sud 91405, Orsay, France
2  Faculté des Sciences de Tunis, LPMC - Campus Universitaire, 1060, Tunis, Tunisia
3  Department of Chemistry, H. C. Ørsted Institute - Universitetsparken 5 DK 2100, Copenhagen, Denmark

received 27 July 2005; accepted in final form 22 September 2005
published online 14 October 2005

The study of the anion ordered $\mth{{\rm (TMTSF)}_{2}{\rm ClO}_{4(1-x)}{\rm ReO}_{4x}}$ solid solution in the limit of a low $\chem{ReO^{-}_{4}}$ substitution level ( $0\leq x\leq 17\%$) has revealed a new and interesting phase diagram. Superconductivity is drastically suppressed as the effect of $\chem{ReO^{-}_{4}}$ non-magnetic point defects increases following the digamma behaviour for usual superconductors in the presence of paramagnetic impurities. Then, no long-range order can be stabilized above 0.1$\un{K}$ in a narrow window of substitution. Finally, an insulating SDW ground state in $\chem{ReO_{4}^{-}}$-rich samples is rapidly stabilized with the decrease of the potential strength leading to the doubling of the transverse periodicity. This extensive study has shown that the superconducting order parameter must change its sign over the Fermi surface.

74.70.Kn - Organic superconductors.
74.62.Dh - Effects of crystal defects, doping and substitution.

© EDP Sciences 2005