Anisotropic energy gaps of iron-based superconductivity from intraband quasiparticle interference in LiFeAs

If strong electron-electron interactions between neighboring Fe atoms mediate the Cooper pairing in iron-pnictide superconductors, then specific and distinct anisotropic superconducting energy gaps Δ_i(k ^→) should appear on the different electronic bands i. Here, we introduce intraband Bogoliubov quasiparticle scattering interference (QPI) techniques for determination of Δ_i(k^→) in such materials, focusing on lithium iron arsenide (LiFeAs). We identify the three hole-like bands assigned previously as γ, α₂, and α₁, and we determine the anisotropy, magnitude, and relative orientations of their Δ_i(k^→): These measurements will advance quantitative theoretical analysis of the mechanism of Cooper pairing in iron-based superconductivity.