Study of Inhomogeneous Organic Superconductors

In many anisotropic superconductors, we have found evidence that they are inhomogeneous superconductors, such as those predicted by Fulde and Ferrell and Larkin and Ovchinnikov (FFLO), at the extremes of low temperature and high magnetic field. A FFLO superconductor has an order parameter with nonzero pair momentum that oscillates periodically as a function of distance, unlike traditional superconductors where the order parameter is uniform. During the last several years, our research group at Clark University has made careful and systematic measurements of quasi-2D organic superconductors that suggest an FFLO state can be stabilized in three different organic conductors if a magnetic field is applied precisely parallel to the conducting layers. We will compare our results with theoretical expressions that we have modified from the current literature, with the goal of extracting quantitative results from the phase diagram data such as the Maki parameter and scattering times. We will also describe improvements to our pulsed magnetic field - tunnel diode oscillator penetration depth apparatus.