Possibility of FFLO state in organic superconductor lambda-(BETS)(2)FeCl4

A magnetic two dimensional organic conductor lambda-(BETS)(2)FeCl4 has a superconducting phase only under high magnetic fields between 18T and 42 T. This field induced superconductivity is qualitatively understood by Jaccarino-Peter effect, and an inhomogeneous superconducting phase, the so-called FFLO phase, whose order parameter oscillates in space, is expected to be stabilized. Under high magnetic fields parallel to the conducting layers, characteristic features in the interlayer resistance are observed, suggesting that the Josephson vortices are strongly pinned at some fields. The results are explained in terms of a commensurability effect between the vortex lattice and the oscillating order parameter.