Impurity controlled Superconductivity/Spin Density Wave interplay in the organic superconductor : (TMTSF)\_2ClO\_4

TL;DR

This paper investigates how impurity-induced defects affect the competition between superconductivity and spin density wave order in the organic superconductor (TMTSF)₂ClO₄, revealing a phase diagram with suppression of superconductivity and emergence of SDW states.

Contribution

It provides new insights into impurity effects on the superconducting and SDW phases in (TMTSF)₂ClO₄, demonstrating the sign-changing nature of the order parameter.

Findings

Superconductivity is suppressed by ReO₄- impurities following digamma behavior.

No long-range order above 0.1K in a narrow substitution window.

ReO₄- rich samples stabilize an insulating SDW ground state.

Abstract

The study of the anion ordered (TMTSF)\_2ClO\_4\_(1-x)ReO\_4\_x, solid solution in the limit of a low ReO\_4- substitution level (0<=x<=17%) has revealed a new and interesting phase diagram. Superconductivity is drastically suppressed as the effect of 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 0.1K in a narrow window of substitution. Finally, an insulating SDW ground state in 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.