Zero Energy Bound States on Nano Atomic Line Defect in Iron-based High Temperature Superconductors

TL;DR

This study investigates the origin of zero energy bound states near line defects in iron-based high-temperature superconductors, revealing their dependence on magnetic order and pairing symmetry through a detailed tight-binding model.

Contribution

It demonstrates that zero energy bound states are induced by weak magnetic order rather than Rashba spin-orbit coupling in Fe atomic line defects.

Findings

Zero energy bound states are linked to weak magnetic order.

Resonance peaks shift with Rashba coupling depending on pairing symmetry.

Order parameter corrections do not affect zero energy peaks.

Abstract

Motivated by recent scanning tunneling microscopy experiments on Fe atomic line defect in iron-based high temperature superconductors, we explore the origin of the zero energy bound states near the endpoints of the line defect by employing the two-orbit four-band tight binding model. With increasing the strength of the Rashba spin-orbit coupling along the line defect, the zero energy resonance peaks move simultaneously forward to negative energy for $s_{+-}$ pairing symmetry, but split for $s_{++}$ pairing symmetry. The superconducting order parameter correction due to As(Te, Se) atoms missing does not shift the zero energy resonance peaks. Such the zero energy bound states are induced by the weak magnetic order rather than the strong Rashba spin-orbit coupling on Fe atomic line defect.