Inhomogeneous interlayer Josephson coupling in κ-(BEDT-TTF)₂Cu(NCS)₂

In a layered superconductor, the interlayer coupling strength determines the spatial variation of the magnetic fields parallel to the layers. Scanning SQUID microscope images of an edge of a single crystal of the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 show regions of inhomogeneous coupling as well as trapped interlayer Josephson vortices. Quantitative modelling of individual isolated vortices indicates an interlayer penetration depth λ⊥ é ∼ 60 μm. Previous bulk measurements that indicated a weaker interlayer coupling may have been dominated by inhomogeneities. © 1999 IOP Publishing Ltd.