Dresden 2011 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: Poster Session Transport
TT 38.8: Poster
Mittwoch, 16. März 2011, 14:00–18:00, P3
Superconductivity-enhanced transport through a carbon nanotube quantum dot with Nb contacts — •Thomas Geiger1, Kicheon Kang1,2, Dmitry Ryndyk3, Andreas Hüttel1, and Christoph Strunk1 — 1Institute for Experimental and Applied Physics, University of Regensburg, Germany — 2Department of Physics, Chonnam National University, Gwangju 500-757, Korea — 3Institute for Theoretical Physics, University of Regensburg, Germany
We present the effect of superconductivity in high quality Nb contacts (Tc = 8.5K, Bc = 4.5T in parallel field) on transport through a SWCNT quantum dot explored by means of high resolution charging diagrams. We find clear transport spectroscopy signatures of the superconductivity in the leads: Over a wide gate range density of states (DOS)-enhanced elastic cotunneling features are observed at an energy of twice the reduced gap of 500 µeV. In some gate regions, Andreev reflection (AR) causes low energy features near the degeneracy points and the contacts’ DOS peaks are reflected in inelastic cotunneling lines.
The magnetic field dependence of these features shows an expected decrease following the gradual suppression of the gap-parameter in the leads. Remarkably, the sub-gap features at certain degeneracy points emerge and show a nonmonotonic temperature dependence: With just precursors visible close to base temperature, a rich structure of the AR features develops much more prominently at a few hundred mK.
Grove-Rasmussen, K., Jørgensen, H. I., Andersen, B. M., Paaske, J., Jespersen, T. S., Nygård, J., Flensberg, K. and Lindelof, P. E.; Phys. Rev. B 79, 134518 (2009)