Modelling & Simulation
Robust determination of the superconducting gap sign structure via quasiparticle interference
Dustin Altenfeld, Ruhr-Universität Bochum, Bochum, GermanyPeter J. Hirschfeld, University of Florida, Gainesville, USAIlya Eremin, Ruhr-Universität Bochum, Bochum, GermanyIgor I. Mazin, Naval Research Laboratory, Washington DC, USA
Using an electronic theory, we present a qualitative description to identify sign changes of the superconducting order parameter via quasiparticle interference (QPI) measurement in Fe-based superconductors (FeSc). In particular, we point out that the temperature dependence of the momentum-integrated QPI data can be used to differentiate between s+- and s++ states in a system with typical iron pnictide Fermi surface. We show that the signed symmetrized and antisymmetrized QPI maps are useful to obtain a characteristic signature of a gap sign change or lack thereof, starting from two-band model up to ab initio based band structure calculation. We further suggest this method as a robust way of the determination of the superconducting gap sign structure in experiment and discuss its application to the LiFeAs compounds.