Unconventional long range triplet proximity effect in planar YBa_2Cu_3O_7/La_0.7Sr_0.3MnO_3/YBa_2Cu_3O_7 Josephson junctions

Abstract

The proximity effect between superconductors and ferromagnets may become long range due to the generation of triplet pairs. The recent finding of a long, one micron-range unconventional Josephson effect between YBa_2Cu_3O_7 high Tc cuprates separated by a half metallic La_0.7Sr_0.3MnO_3 manganite ferromagnet has uncovered a novel unconventional triplet proximity effect. In this paper, we examine the temperature dependence of the critical current in planar Josephson junctions. We find that the critical current-normal resistance product follows the predictions of traditional superconductor-normal metal-superconductor junctions, which implies that triplet pairs in a ferromagnet are transported in the diffusive limit similarly to singlet pairs in a normal metal. This result calls for theoretical studies of the new triplet Josephson effect and underlines its potential in future superconducting spintronics.