Study of over-doped thin film LSCO with scanning squid microscopy*

The high-temperature superconductor cuprates, with their complex phase diagram, offer an intriguing playground for testing new theories. It has recently been proposed that homogeneous, intermediate-strength disorder is responsible for several previously unexplained features of the superfluid density in the overdoped cuprates [1]. To test the validity of this picture, we have characterized the spatial homogeneity of zero-frequency superfluid density using scanning-SQUID microscopy. We performed simultaneous magnetometry and susceptometry scans of various-doped LSCO epitaxially grown on LSAO by MBE. We observed higher than expected critical temperature (45K for x=0.23) and spatial inhomogeneity of superfluid density (variation by a factor of 10 across 3mm). Therefore, local variation of superfluid density in these LSCO thin film samples has to be taken into account for future experiments.
[1] N. R Lee-Hone et al., Phys. Rev. B 98, 054506 (2018)