Magnetic and superconducting structures near twin boundaries in low doped Fe-pnictides

TL;DR

This study investigates how twin boundaries in electron-doped Ba(Ca)(FeAs)$_2$ superconductors influence magnetic and superconducting orders, revealing that certain TBs enhance superconductivity while others suppress it.

Contribution

It provides a detailed analysis of the spatial distribution of magnetic and superconducting orders near different types of twin boundaries in low-doped Fe-pnictides.

Findings

Magnetic domain walls form at TBs with 90° lattice rotation.

Superconductivity is enhanced at TBs with 90° lattice rotation.

Superconductivity is suppressed at asymmetrical As atom TBs.

Abstract

The effects of twin boundaries (TBs) on the complex interaction between magnetism and superconductivity in slightly electron-doped Ba(Ca)(FeAs)$_2$ superconductors are investigated. The spatial distributions of the magnetic, superconducting and charge density orders near two different types of TBs are calculated. We find that TBs corresponding to a 90$^\circ$ lattice rotation in the a-b plane enable magnetic domain walls to form with only a small effective Coulomb interaction between valance electrons, and that superconductivity is enhanced at such TBs. Contrastingly, we find that superconductivity is suppressed at TBs corresponding to an asymmetrical placement of As atoms with respect to the Fe atoms in the a-b plane.