Quasiparticle Interference in Fe-based Superconductors Based on a Five-Orbital Tight-Binding Model

Abstract

We investigate the quasiparticle interference (QPI) in Fe-based superconductors in both the $s_{++}$-wave and $s_{\pm }$-wave superconducting states on the basis of the five-orbital model. In the octet model for cuprate superconductors with $d_{x^2-y^2}$-wave state, the QPI signal due to the impurity scattering at $q=k_i-k_j$ ($E=|\Delta (k_i)|$, $i=1\sim 8$) disappears when the gap functions at $k_i$ and $k_j$ have the same sign. However, we show that this extinction rule does not hold in Fe-based superconductors with fully-gapped $s$-wave state. The reason is that the resonance condition $E=|\Delta (k_i)|$ is not satisfied under the experimental condition for Fe-based superconductors. We perform the detailed numerical study of the QPI signal using the $T$-matrix approximation, and show that the experimentally observed QPI peak around $q_2=(\pi ,0)$ can be explained on the basis of both the $s_{++}$-wave and $s_{\pm }$-wave states. Furthermore, we discuss the magnetic field dependence of the QPI by considering the Zeeman effect, and find that the field-induced suppression of the peak intensity around $q_2$ can also be explained in terms of both the $s_{++}$-wave and $s_{\pm }$-wave states.

10 pages, 8 figures

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• Revealing sign-reversal $s^{+-}$-wave pairing by quasiparticle interference in the heavy-fermion superconductor CeCu${}_2$Si${}_2$
• Investigation of magnetic phases in parent compounds of Iron-chalcogenides via quasiparticle scattering interference