Penetration of Andreev bound states into the ferromagnet in a SrRuO$_{3}$/(110)YBa$_2$Cu$_3$O$_{7-\delta}$ bilayer: a scanning tunneling spectroscopy study

TL;DR

This study uses scanning tunneling spectroscopy to observe how Andreev bound states penetrate a ferromagnetic layer in a bilayer, revealing split zero bias conductance peaks caused by induced magnetization and spin polarization.

Contribution

It provides experimental evidence of Andreev bound state penetration into a ferromagnet, confirming theoretical predictions about induced magnetization effects.

Findings

Split zero bias conductance peaks in ferromagnet density of states

Splitting caused by induced magnetization at the superconductor interface

Imbalance in peaks attributed to ferromagnet spin polarization

Abstract

Scanning tunneling spectroscopy of thin epitaxial $SrRuO_{3}/(110)YBa_2Cu_3O_{7-\delta}$ ferromagnet/superconductor bilayers, reveal 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.