Directly Visualizing Bogoliubov Quasiparticle Interference of LiFeAs: a Way Toward Understanding Superconductivity in Iron Pnictides

ORAL

Abstract

Imaging quasiparticle interference (QPI) is a way to probe the electronic states of a wide range of materials. In superconductors, QPI of Bogoliubov excitations is directly sensitive to the sign changes of the superconducting order parameter. In this talk, I present our investigation of QPI in superconducting LiFeAs by means of scanning tunneling microscopy/spectroscopy, angle resolved photoemission spectroscopy, and multi-orbital tight binding calculations. Using this combination we identify intra- and interband scattering vectors between the hole ($h$) and electron ($e$) bands in the QPI maps. Bogoliubov QPI, with a clear antisymmetric phase at positive and negative bias voltages near the superconducting gap, is revealed in the spatial modulations of the local density of states. The observation of both h-h and e-h scattering intensity variations is exploited using scattering selection rules for Bogoliubov quasiparticles. From this we infer an $s+-$ gap structure, where a sign change occurs in the superconducting order parameter between the $e$ and $h$ bands.

*Killam, Alfred P. Sloan, NSERCs Steacie Memorial Fellowship, the CRC Program, CFI, NSERC, and CIFAR Quantum Materials

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Authors

  • Shun Chi

    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • Steven Johnston

    • Department of Physics and Astronomy, Univ. of British Columbia, Vancouver, Canada
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia
    • University of Tennessee

  • G. Levy

    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • S. Grothe

    • Department of Physics and Astronomy, Univ. of British Columbia, Vancouver, Canada
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • R. Szedlak

    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • B. Ludbrook

    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • Ruixing Liang

    • The University of British Columbia
    • University of British Columbia
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • P. Dosanjh

    • Department of Physics and Astronomy, Univ. of British Columbia, Vancouver, Canada
    • The University of British Columbia
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • Sarah Burke

    • Department of Physics and Astronomy, Department of Chemistry, Univ. of British Columbia, Vancouver, Canada
    • Department of Physics \& Astronomy and Department of Chemistry, University of British Columbia
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia
    • University of British Columbia
    • Univ British Columbia

  • Andrea Damascelli

    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia
    • University of British Columbia, Vancouver, Canada

  • Doug Bonn

    • The University of British Columbia
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia
    • Univ British Columbia
    • University of British Columbia

  • Walter Hardy

    • The University of British Columbia
    • University of British Columbia
    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia

  • Y. Pennec

    • Department of Physics and Astronomy, University of British Columbia; Quantum Matter Institute, University of British Columbia