Comparison among superconducting models for β-ET4[(H30)Fe(C204)3]-C6H5Br single crystals by scanning tunnelling spectroscopy

Single crystals of the novel superconductor beta''-(BEDT-TTF)4[(H3O)Fe(C2O4)3]*C6H5Br charge-transfer salt were studied using a scanning tunnelling microscope. The measured samples have an onset critical temperature of about 4.0 K. Features often reported on similar compounds were observed in the tunnelling spectra at 1.4 K. STS spectra are compared with several models for the superconducting density of states. Our analysis evidences inhomogeneous superconductivity and indicates that the presence of a magnetic layer into the sample plays a role in determining the superconducting spectroscopic features.