Pressure-dependent topological superconductivity on the surface of FeTe_0.5Se_0.5

FeTe1-x Se x is a family of iron-based superconductors with its critical temperature (T c) dependent on the composition of Se. A well-known T c is 14.5 K for x = 0.45, which exhibits an s-wave superconducting gap between the topological superconducting surfaces states. Exchange interaction between the electrons has been proposed as the mechanism behind the formation of Cooper pairs for the sample of FeTe0.5Se0.5. In this article we provide further proof that exchange interaction, and hence the associated T c, depends on the applied pressure on FeTe0.5Se0.5. Using density functional calculations for electrons and phonons and the Bardeen-Cooper-Schrieffer (BCS) theory for superconductivity, we found that T c and superconducting gap for FeTe0.5Se0.5 soars under increasing compression, consistent with the results of experiment.