Crossed andreev in d-wave superconductor-ferromagnet junctions in the vicinity of domain walls
Tal Kirzhner , Gad Koren
Measurements of the differential conductance spectra of YBa2Cu3O7−δ-SrRuO3 and YBa2Cu3O7−δ-La0.67Ca0.33MnO3 ramp-type junctions along the node and antinode directions are reported. Interpretation of the results in terms of crossed Andreev reflection effect and induced triplet superconductivity are discussed. The results are consistent with a crossed Andreev reflection effect only in YBa2Cu3O7−δ-SrRuO3 junctions where the domain-wall width of SrRuO3 is comparable with the coherence length of YBa2Cu3O7−δ. No such effect was observed in the YBa2Cu3O7−δ-La0.67Ca0.33MnO3 junctions, which is inline with the much larger (×10) domain-wall width of La0.67Ca0.33MnO3. We also show that crossed Andreev exists only in the antinode direction. Furthermore, we find evidence that crossed Andreev in YBa2Cu3O7−δ junctions is not sensitive to nanometer-scale interface defects, suggesting that the length scale of the crossed Andreev effect is larger than the coherence length, but still smaller than the La0.67Ca0.33MnO3’s domain-wall width.