Behavior of vortices near twin boundaries in underdoped $Ba(Fe_{1-x}Co_{x})_{2}As_{2}$

TL;DR

This study uses scanning SQUID microscopy to show that vortices in Ba(Fe1-xCox)2As2 avoid twin boundaries, moving parallel to them due to increased superfluid density, which may enhance critical currents in these superconductors.

Contribution

It reveals the vortex behavior near twin boundaries in pnictide superconductors and links it to superfluid density variations, providing insight into vortex dynamics and critical current enhancement.

Findings

Vortices avoid pinning on twin boundaries.

Vortices tend to move parallel to twin boundaries.

Enhanced superfluid density is observed on twin boundaries.

Abstract

We use scanning SQUID microscopy to investigate the behavior of vortices in the presence of twin boundaries in the pnictide superconductor Ba(Fe1-xCox)2As2. We show that the vortices avoid pinning on twin boundaries. Individual vortices move in a preferential way when manipulated with the SQUID: they tend to not cross a twin boundary, but rather to move parallel to it. This behavior can be explained by the observation of enhanced superfluid density on twin boundaries in Ba(Fe1-xCox)2As2. The observed repulsion from twin boundaries may be a mechanism for enhanced critical currents observed in twinned samples in pnictides and other superconductors.