Superconducting properties of highly oriented Fe1.03Te0.55Se0.45 with excess Fe

Highly oriented Fe1.03Te0.55Se0.45 crystal with T c ∼ 14.4 K was grown through Optical Zone-Melting Technique. Resistivity versus temperature under various magnetic fields was measured. The upper critical field μ 0 H c 2 estimated from the WHH equation reaches 42.6 T, which is in good agreement with experimental results. The Ginzburg–Landau (GL) coherence length at zero temperature was estimated to be 27.77–29.33 Å. The activation energy determined from the Arrhenius dependence of the resistivity reaches ∼103 K. Due to its relatively low T c compared with FeAs superconductors and high- T c cuprates, we suggest that the high activation energy should be attributed to the existence of excess Fe located in FeTe(Se) layers, which might induce vacancies into the system. The e–ph coupling parameter is estimated to be 1.40, revealing that Fe1.03Te0.55Se0.45 belongs to the strong electron–phonon coupling system.