Anisotropic field dependence of the electronic transport in superconducting FeSe thin films

Electronic transport measurements were carried out on c-axis oriented epitaxial FeSe thin films in static magnetic fields up to 14 T parallel to the crystallographic c-axis and parallel to the ab-plane. The temperature dependence of the upper critical fields B-c2(c) and B-c2(ab) was determined from the field dependence of the resistivity. While B-c2(c) was orbitally limited, the larger B-c2(ab) was paramagnetically limited. The anisotropy gamma(B) was decreasing with decreasing temperature and revealed a pseudoisotropic behaviour towards zero temperature. This temperature dependence is indicative of the multiband character of FeSe. From measurements of the temperature- and field-dependent critical current densities the effective depinning or irreversibility field B-c2* was obtained, and its angular dependence yielded the effective mass anisotropy gamma(m). The temperature dependence of gamma(m), which was different from that of gamma(B), can be considered as another signature of multiband FeSe.