Unconventional superconductivity in a highly two-dimensional organic charge transfer salt

Although many organic superconductors can be produced via charge transfer salts of the organic molecule BEDT-TTF, the new compound β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown 6 with superconducting onset at 4 K stands out as having a particularly strong 2D character due to an unusually thick anion layer separating the metallic BEDT-TTF layers. This produces an extremely good example of a highly anisotropic superconductor whose 2D superconducting vortex properties are expected to be well described by Berezinskii-Kosterlitz-Thouless physics. Existing data on the upper critical field for in-plane field orientation exceeds the Pauli limit at low temperature, pointing towards an unconventional character for the superconductivity. This proposal will use TF-muSR to explore the superconducting phase diagram and the vortex properties of the mixed state of this novel superconductor and compare its properties against those of other molecular organic superconductors.