Local variations of superfluid density in twinned high temperature superconductors

5 Jan 2011, 16:30
40m
FB54

FB54

Speaker

Beena Kalisky (Stanford U.) (Stanford)

Description

We use scanning SQUID microscopy to investigate local variations in the diamagnetic susceptibility in twinned samples of two families of high temperature superconductors. In Ba(Fe1-xCox)2As2 of the pnictides we observe increased diamagnetic susceptibility on the twin boundaries in underdoped, but not overdoped, single crystals. Vortex behavior near the twin boundaries reveals that vortices avoid pinning on the twins, 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. In YBa2Cu3O7-x of the cuprates vortices have been observed to line up on the twin boundaries. I will show our preliminary data on direct measurement of the susceptibility near twin boundaries in YBa2Cu3O7-x . I will also show and discuss SQUID imaging of vortices at very low fields in both systems.

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