Abstract
We study momentum and energy dependencies of the quasiparticle interference (QPI) response function in multiband superconductors in the framework of the strong-coupling Eliashberg approach. Within an effective two-band model we study the s± and s++ symmetry cases, corresponding to opposite or equal signs of the order parameters in the bands. We demonstrate that the momentum dependence of the QPI function is strikingly different for s± and s++ symmetries of the order parameter at energies close to the small gap. At the same time, the QPI response becomes indistinguishable for both symmetries at higher energies around the large gap. This result may guide future experiments on probing pairing symmetry in iron pnictides as well as in other unconventional superconductors.
Highlights
Recent developments of the tunneling spectroscopy technique have allowed to make a great progress in elucidating the physics of high-temperature superconductors[1,2,3,4]
We study the evolution of the momentum and the energy dependence of the quasiparticle interference (QPI) response function I(ω, q), with the change of the band parameters viz., the ellipticity of electron-like bands ε, the Fermi energy mismatch δμ between the bands and momentum parameter vbq
Within an effective two band model it was shown that the more informative is a behavior of this function near the at energies close to the small gap
Summary
The single-particle correlation functions, including I(q, ω), in multiband systems with strong coupling interaction can be found by using the multiband extension of the Eliashberg theory[20,21,22,23,24,25,26,27]. Q is the vector that connects the centres of the pockets situated at Γ and the M points, respectively, ε characterizes the ellipticity of the electron bands (as shown in Fig. 2) and θ is the angle between p and x -axis. This expansion is valid for the momenta p that lie close to the Fermi surface and the ellipticity parameter obeys the tcoonindtirtoiodnuctheatth|eε|ch emvFicpaFl. To keep the generality we will use the notation for the pockets as a and b.
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