CC BY 3.0 UnportedYuan, F.Grinenko, V.Iida, K.Richter, S.Pukenas, A.Skrotzki, W.Sakoda, M.Naito, M.Sala, A.Putti, M.Yamashita, A.Takano, Y.Shi, Z.Nielsch, K.Hühne, R.2020-07-132020-07-132018https://doi.org/10.34657/3523https://oa.tib.eu/renate/handle/123456789/4894Revealing the universal behaviors of iron-based superconductors (FBS) is important to elucidate the microscopic theory of superconductivity. In this work, we investigate the effect of in-plane strain on the slope of the upper critical field H c2 at the superconducting transition temperature T c (i.e. -dH c2/dT) for FeSe0.7Te0.3 thin films. The in-plane strain tunes T c in a broad range, while the composition and disorder are almost unchanged. We show that -dH c2/dT scales linearly with T c, indicating that FeSe0.7Te0.3 follows the same universal behavior as observed for pnictide FBS. The observed behavior is consistent with a multiband superconductivity paired by interband interaction such as sign change s ± superconductivity.enghttps://creativecommons.org/licenses/by/3.0/530Iron compoundsSelenium compoundsSingle crystalsStrainSuperconducting filmsSuperconducting transition temperatureTechnetiumTellurium compoundsThin filmsEffect of InIn-plane strainsMicroscopic theoryMultiband superconductivitySign-changeUniversal behaviorsUniversal scalingUpper critical fieldsIron-based SuperconductorsFe-based superconductorsthin filmupper critical fieldsArticle