Enhancement of the superconducting transition temperature in FeSe epitaxial thin films by anisotropic compression

Abstract

In order to investigate the effects of in-plane strain on the superconductivity of FeSe, epitaxial thin films of FeSe were fabricated on CaF2 substrates. The films are compressed along the a-axis and their superconducting transition temperatures Tczero reach 11.4 K, which is approximately 1.5 times higher than that of bulk crystals. The Tc values are weakly dependent on the ratio of the lattice constants, c/a, compared to that of Fe(Se, Te). Our results indicate that even a binary system FeSe has room for improvement, and will pave the way for the application of Fe-based superconductors.