Evidence for spin-polarized bound states in semiconductor-superconductor-ferromagnetic-insulator islands

We report Coulomb blockade transport studies of semiconducting InAs nanowires grown with epitaxial superconducting Al and ferromagnetic insulator EuS on overlapping facets. Comparing experiment to a theoretical model, we associate cotunneling features in even-odd bias spectra with spin-polarized Andreev levels. Results are consistent with zero-field spin splitting exceeding the induced superconducting gap. Energies of subgap states are tunable on either side of zero via electrostatic gates.

Automated summary

Through Coulomb blockade transport studies, we found that cotunneling features in the even-odd bias spectra of nanowires grown with superconducting Al and ferromagnetic insulator EuS on overlapping facets are associated with spin-polarized Andreev levels. Experimental results indicate that the zero-field spin splitting exceeds the induced superconducting gap and the energy of subgap states can be controlled by electrostatic gates.