Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 28: Focused Session: Spin Transport and Coherence in Emerging Materials
MA 28.1: Topical Talk
Mittwoch, 25. März 2009, 14:45–15:15, HSZ 101
Gate-tunable magnetic exchange and giant g-factor fluctuations in InAs nanowire quantum dots — Szabolcs Csonka1, Lukas Hofstetter1, Frank Freitag1, •Christian Schönenberger1, Thomas S. Jespersen2, Martin Aagesen2, and Jesper Nygard2 — 1Department of Physics, Univ. of Basel, CH-4056 Basel, Switzerland — 2Nano-Science Center, Niels-Bohr Institute, Univ. of Copenhagen, DK-2100 Copenhagen, Denmark
We use the spin-1/2 Kondo effect to measure the field-induced splitting of the spin-doublet, and hence the g-factor. We do this in hybrid quantum dots using both normal (N), ferromagnetic (F) and superconducting (S) contacts. Unlike to previous studies, the g-factors of neighboring states can scatter between 2 and 18 and can therefore be even larger than in the bulk (g=15). We demonstrate further the electric gate tunability of the g-factor in a single charge state. When using F contacts, a zero-field splitting is induced. This prox-imity induced exchange field has recently been measured for the first time by Hauptmann et al. (Nature Physics Vol 4, (2008)) in carbon nanotubes. Here, we show the same effect in a semiconducting nanowire, demonstrating that this effect is universal. Employing a pair of S and F contacts, the proximity-induced exchange shows up as a minigap in superconducting spectroscopy.
This work has been supported by the Swiss NSF, the NCCR on Nanoscale Science, and the Danish Natural Science Research Council. S. Csonka is a grantee of the Marie Curie Fellowship.