Effect of Bending Strain on Superconducting Transition Temperature of FeSe0.5Te0.5 Thin Films

Iron chalcogenide superconductors of iron-based superconductor (IBS) family, have attracted much attention recently. For the study of unconventional superconductors, uniaxial strain effect plays an important role with the actuator method as the main approach with quite limited strain. This is unfavorable for uncovering the full behavior and the understanding of strain effect. Here, FeSe0.5Te0.5 thin films are grown on mica to induce strains via different bending states with strain reaching 2%, roughly an order of magnitude larger than that of the actuator method. Both the lattice parameters and transport properties show changes with strain. The variation of superconducting transition temperature (T-c) with compressive strain shows a nonmonotonic change with a maximum. Theoretical calculations suggest that superconductivity is influenced by the spin fluctuation in different bending states. The nonmonotonic change of T-c with compressive strain can be understood by considering the strain-dependent competition between the spin fluctuation and nematic order. This work provides valuable insights for understanding the superconducting mechanism of IBS and also paves the way for exploring unconventional superconductivity via bending strains.