T42: Topological Superconductivity: Theory

Thu. March 9, 12:06 p.m. – 12:18 p.m. PST

Room 318

FeTe_1-xSe_x is a family of iron-based superconductors with its critical temperature (Tc) 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 associated with topological surfaces states. Exchange interaction between the electrons has been proposed as the mechanism behind the formation of singlet Cooper pairs for the sample of FeTe_0.5Se_0.5. We provide further proof that exchange interaction, and hence the associated T_c, depends on the applied pressure on FeTe_0.5Se_0.5. Using DFT calculation for electrons and phonons and the Bardeen-Cooper-Schrieffer (BCS) theory for superconductivity, we found that T_c and superconducting gap for FeTe_0.5Se_0.5 soars under increasing compression, consistent with the results of experiment. UTe₂ is a typical triplet superconductor. We will discuss how DFT calculation of exchange integrals and phonon bands affects its T_c and superconducting gap.