Diamagnetic Vortex Barrier Stripes in Underdoped $BaFe_2(As_{1-x}P_x)_2$

TL;DR

This study uses magnetic force microscopy to reveal that in underdoped BaFe2(As1-xPx)2, superconductivity is enhanced along twin boundary stripes that act as vortex barriers, with these stripes disappearing near the transition temperature.

Contribution

It demonstrates the existence of dynamic diamagnetic vortex barrier stripes in underdoped BaFe2(As1-xPx)2 and explores their behavior and relation to similar phenomena in related compounds.

Findings

Stripes of enhanced diamagnetic response repel vortices.

Stripes disappear near the superconducting transition temperature.

Stripes can move when warming the sample.

Abstract

We report magnetic force microscopy (MFM) measurements on underdoped $BaFe_2(As_{1-x}P_x)_2$ ($x=0.26$) that show enhanced superconductivity along stripes parallel to twin boundaries. These stripes of enhanced diamagnetic response repel vortices when we cool in a finite magnetic field and act as barriers when we drag vortices with the magnetic MFM tip. The stripes disappear when we warm the sample towards the superconducting transition temperature. We show that stripes can move when we warm the sample and comment on the relationship between the stripes and similar stripes observed previously in $Ba(Fe_{1-x}Co_x)_2As_2$.