Penetration of Andreev bound states into the ferromagnet in a SrRu O3 / (110) Y Ba2 Cu3 O7-δ bilayer: A scanning tunneling spectroscopy study

Scanning tunneling spectroscopy of thin epitaxial SrRu O3 / (110) Y Ba2 Cu3 O7-δ ferromagnet/superconductor bilayers reveals a clear penetration of the Andreev bound states into the ferromagnetic layer. The penetration is manifested in the density of states of the ferromagnet as a split zero-bias conductance peak with an imbalance between peak heights. Our data indicate that the splitting occurs at the superconductor side as a consequence of induced magnetization, confirming recent theoretical predictions. The imbalance is attributed to the spin polarization in the ferromagnet.