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Quasiparticle interference in Fe-based superconductors based on a five-orbital tight-binding model

Youichi Yamakawa and Hiroshi Kontani, Phys. Rev. B 92, 045124 (2015).

We investigate the quasiparticle interference (QPI) in Fe-based superconductors in both the s++-wave and s±-wave superconducting states on the basis of the five-orbital model. In the octet model for cuprate superconductors with dx2−y2-wave state, the QPI signal due to the impurity scattering at q=kikj (E=|Δ(ki)|, i=1−8) disappears when the gap functions at ki and kj 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=|Δ(ki)| 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 q2=(π,0) can be explained on the basis of both the s++-wave and s±-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 q2 can also be explained in terms of both the s++-wave and s±-wave states.