Theory of Mixed-State Effect on Quasiparticle Interference in Iron-based Superconductors

TL;DR

This paper investigates how magnetic fields affect quasiparticle interference in iron-based superconductors with different pairing symmetries, using large-scale Bogoliubov-de Gennes equations, and finds evidence supporting $s_{}$ pairing over s-wave.

Contribution

The study rigorously models vortex effects in quasiparticle interference, providing a more accurate comparison with experiments and excluding s-wave pairing in favor of $s_{}$ symmetry.

Findings

Results agree with experiments for $s_{}$ pairing

Contradicts experimental observations for s-wave pairing

Vortex effects modeled rigorously for robustness

Abstract

Based on a phenomenological model with $s_{\pm}$ or s-wave pairing symmetry, the mixed-state effect on quasiparticle interference in iron-based superconductors is investigated by solving large-scale Bogoliubov-de Gennes equations based on the Chebyshev polynomial expansion. Taking into account the presence of magnetic field, our result for the $s_{\pm}$ pairing is in qualitative agreement with recent scanning tunneling microscopy experiment while for the s-wave pairing, the result is in apparent contradiction with experimental observations, thus excluding the s-wave pairing. Furthermore, we treat the effect of vortices rigorously instead of approximating the vortices as magnetic impurities, thus our results are robust and should be more capable of explaining the experimental data.