Phase-sensitive evidence for dx2-y2-pairing symmetry in the parent-structure high-Tc cuprate superconductor Sr1-xLaxCuO2

TL;DR

This study provides phase-sensitive evidence that the superconducting order parameter in Sr1-xLaxCuO2, a parent-structure high-Tc cuprate, has dx2-y2-wave symmetry, suggesting this is inherent to cuprate superconductivity.

Contribution

First phase-sensitive measurement of the order parameter symmetry in Sr1-xLaxCuO2 using grain boundary Josephson junctions, confirming dx2-y2-wave symmetry in the parent high-Tc cuprate.

Findings

Superconducting order parameter in Sr1-xLaxCuO2 is dx2-y2-wave.

High-quality films of Sr1-xLaxCuO2 were successfully fabricated.

The dx2-y2 symmetry appears to be inherent to cuprate superconductivity.

Abstract

Even after 25 years of research the pairing mechanism and - at least for electron doped compounds - also the order parameter symmetry of the high transition temperature (high-Tc) cuprate superconductors is still under debate. One of the reasons is the complex crystal structure of most of these materials. An exception are the infinite layer (IL) compounds consisting essentially of CuO2 planes. Unfortunately, these materials are difficult to grow and, thus, there are only few experimental investigations. Recently, we succeeded in depositing high quality films of the electron doped IL compound Sr1-xLaxCuO2 (SLCO), with x approximately 0.15, and on the fabrication of well-defined grain boundary Josephson junctions (GBJs) based on such SLCO films. Here we report on a phase sensitive study of the superconducting order parameter based on GBJ SQUIDs from a SLCO film grown on a tetracrystal substrate. Our results show that also the parent structure of the high-Tc cuprates has dx2-y2-wave symmetry, which thus seems to be inherent to cuprate superconductivity.