Robust measurement of superconducting gap sign changes via quasiparticle interference: an application to 111 compounds

ORAL

Abstract

While quasiparticle interference (QPI) measurements based on scanning tunneling spectroscopy are often proposed as definitive tests of gap structure, the analysis typically relies on details of the model employed. Here using the simplified two-band model system we propose, that the temperature dependence of momentum-integrated QPI data can be used to identify gap sign changes in a qualitative way, and present an illustration for $s_{\pm}$ and $s_{++}$ states in a system with typical Fe-pnictide Fermi surface. Using ARPES derived band structures within 10 orbital model Hamiltonian we analyze the QPI spectra in LiFeAs and Co-doped NaFeAs compounds and show that the sign-changing gap can be clearly identified using non-magnetic impurity scattering.

*P.J.H. was supported by NSF-DMR-1005625, and I.I.M. by the U.S. Office of Naval Research through the Naval Research Laboratory's Basic Research Program. The work of DA and IE was supported by the Focus Program 1458 Eisen-Pniktide of the DFG

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Authors

  • Ilya Eremin

    • Institut f\"ur Theoretische Physik III, Ruhr-Universit\"at Bochum, D-44801 Bochum, Germany

  • Dustin Altenfeld

    • Institut f\"ur Theoretische Physik III, Ruhr-Universit\"at Bochum, D-44801 Bochum, Germany

  • Peter Hirschfeld

    • Department of Physics, University of Florida, Gainesville, Florida 32611, USA

  • Igor Mazin

    • Code 6393, Naval Research Laboratory, Washington, DC 20375, USA