Small-q phonon-mediated superconductivity in organic κ-BEDT-TTF compounds

Abstract

We propose a mew picture for superconductivity in $\kappa -(BEDT-TTF{)}_{2}X$ salts arguing that small-{\bf q} electron-phonon scattering dominates the pairing. We reproduce the distinct X-shaped d-wave gap reported recently by magnetooptic measurements and we argue that the softness of the momentum structure of the gap and the near degeneracy of s- and d-wave gap states may be at the origin of the experimental controversy about the gap symmetry. We show that a magnetic field applied parallel to the planes may induce extended gapless-regions on the FS accounting for the experimental signatures of a Fulde-Ferrel-Larkin-Ovchinikov state and it may induce gap symmetry transitions as well.

4 pages and 7 figures

References in corpus (1)

• Observation of the Fulde-Ferrell-Larkin-Ovchinnikov state in the quasi-two-dimensional organic superconductor $\kappa$-(BEDT-TTF)${}_2$Cu(NCS)${}_2$

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