抄録
The upper critical field Hc2 of the layered superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl under the pressure of 1-2 kbar has been studied under the magnetic field applied parallel to the superconducting plane. The Hc2 changes with temperature almost linearly and exceeds the BCS Pauli paramagnetic limit near 0 K. By taking into account the sharp local minimum of the resistance in the parallel orientation of the magnetic field to the layer, the Hc2 is discussed in relation to the inhomogeneous order-parameter state. The coherence lengths are determined as 20±3 and 0.8±0.2 nm parallel and perpendicular to the layer from the temperature dependence of Hc2 near Tc, while the corresponding lengths are 13±1 and 1.3±0.1 nm from Hc2 at 0 K, respectively, for the crystal under the pressure of 1.9 kbar. The origin of the difference is discussed.
