Fe-based superconducting thin films on metallic substrates: Growth, characteristics, and relevant properties

The discovery of Fe-based superconductors (FBS) as the second class of high-temperature superconducting transition (high-Tc) materials after the cuprates generated a significant impact on the community of fundamental and applied superconductivity research. Whenever a new class of high-Tc superconducting materials is discovered, a lot of effort is devoted to growing single crystals and epitaxial thin films for exploring basic physical quantities. Although several properties of FBS are similar to the cuprates (large upper critical fields, as a consequence short coherence lengths and small carrier density), others are distinctly different. For instance, in FBS, the symmetry of the superconducting order parameter is most likely not a d-wave but an s±-wave, depending on the stoichiometry, crystallographic system, and doping level. Additionally, the critical current densities of FBS are less sensitive to the presence of grain boundaries (GBs) than those of the high-Tc cuprates. These features are highly benefic...