Strain-driven attenuation of superconductivity in heteroepitaxial perovskite/YBCO/perovskite thin films

TL;DR

This study investigates how heteroepitaxial strain, rather than magnetism, causes suppression of superconductivity in thin YBCO layers within various perovskite heterostructures, revealing strain as the key factor affecting $T_c$.

Contribution

It demonstrates that heteroepitaxial strain, not magnetic proximity effects, is primarily responsible for superconductivity attenuation in $c$-axis YBCO heterostructures.

Findings

Superconducting $T_c$ decreases with thinner YBCO layers.

Strain, not magnetism, drives $T_c$ suppression.

Long-range $T_c$ attenuation is linked to heteroepitaxial strain.

Abstract

To distinguish between the effects of strain and magnetism on the superconductivity in $c$-axis La$_{2/3}$Ca$_{1/3}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-\delta}$ (LCMO/YBCO) heterostructures, we study perovskite/YBCO/perovskite thin films using either ferromagnetic LCMO or paramagnetic LaNiO$_3$ (LNO) as perovskite. For a lattice-symmetry matched comparison, we also use orthorhombic PrBa$_2$Cu$_3$O$_{7-\delta}$ (PBCO) in place of the pseudocubic perovskites. Unlike PBCO/YBCO/PBCO, both LCMO/YBCO/LCMO and LNO/YBCO/LNO trilayers show strong attenuation of the superconducting $T_c$ as YBCO layer thickness is reduced from 21.4 to 5.4 nm. Our results indicate that heteroepitaxial strain, rather than long-range proximity effect, is responsible for the long length scales of $T_c$ attenuation observed in $c$-axis LCMO/YBCO heterostructures.