Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.63: Poster
Wednesday, March 28, 2012, 15:00–19:00, Poster B
Proximity effect between a ferromagnetic insulator and a superconductor — •Michael J. Wolf1, Florian Hübler1,2, Christoph Sürgers3, Detlef Beckmann1, and Hilbert v. Löhneysen2,3 — 1Institut für Nanotechnologie, KIT — 2Institut für Festkörperphysik, KIT — 3Physikalisches Institut, KIT
Electron transfer through spin-active interfaces can be modeled by the transmission amplitudes
and a relative phase shift between spin-up and spin-down wavefunctions, the spin-mixing angle [1].
Recently, Andreev bound states have been observed in F/S tunnel contacts
which imply a non-zero spin-mixing angle of the ultrathin F/S barrier [2].
In order to separate the spin-active interface from the detector tunnel contact,
we have fabricated normal metal / superconductor tunnel contacts on top of a ferromagnetic insulator.
We prepared EuS thin films (d ≈ 20 nm) on top of Si(111) substrates by means of e-beam evaporation and created
Al / Al-Oxide / Cu tunnel contacts by means of shadow evaporation.
In an applied magnetic field, the tunnel spectra show an enhanced Zeeman splitting
which is due to the presence of the exchange field of the EuS layer [3].
Furthermore, we observe small peaks in the subgap region of the tunnel spectra which may be attributed to
Andreev bound states due to a non-zero spin-mixing angle at the EuS / Al interface.
The results suggest the use of EuS thin films for generating equal-spin triplet superconductivity.
T.Tokayasu et al. Phys. Rev. B 38, 8823 (1988)
F. Hübler et al. arXiv:1012.3867 (2010)
X. Hao et al. Phys. Rev. Lett. 67, 1342 (1991)