Enhanced superfluid density on twin boundaries in Ba(Fe1-xCox)2As2

TL;DR

This study uses SQUID microscopy to reveal enhanced superfluid density along twin boundaries in underdoped Ba(Fe1-xCox)2As2, linking local strain and magnetism to improved critical current mechanisms.

Contribution

It demonstrates the presence of increased superfluid density on twin boundaries in underdoped samples and explores their impact on vortex behavior and critical currents.

Findings

Enhanced diamagnetic susceptibility stripes in underdoped crystals

Vortices avoid crossing or pinning on stripes

Twin boundaries influence superfluid density and vortex dynamics

Abstract

Superconducting quantum interference device (SQUID) microscopy shows stripes of increased diamagnetic susceptibility in underdoped, but not overdoped, single crystals of Ba(Fe1-xCox)2As2. These stripes of increased diamagnetic susceptibility are consistent with enhanced superfluid density on twin boundaries. Individual vortices avoid pinning on or crossing the stripes, and prefer to travel parallel to them. These results indicate a relationship between superfluid density, local strain, and frustrated magnetism, and demonstrate two mechanisms for enhancing critical currents.