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O: Fachverband Oberflächenphysik

O 4: Transport: Quantum Dots, Quantum Wires, Point Contacts I (TT jointly with O)

O 4.8: Talk

Monday, March 31, 2014, 11:30–11:45, BEY 81

In gap and out of gap features in the cotunneling spectroscopy of a superconductor coupled quantum dot — •Sascha Ratz and Milena Grifoni — Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany

We present a nonequilibrium real-time diagrammatic theory for the systematic investigation of low temperature quantum transport properties of a superconductor contacted quantum dot in an individual single wall carbon nanotube. In the low temperature regime particle transport is dominated by cotunneling and Andreev reflection processes. As recent experiments show, elastic/inelastic cotunneling features are clearly visible inside the Coulomb blockade regime, sharpened by the superconducting leads. The proximity induced higher order Andreev reflection processes result in subgap features, however. Temperature dependent measurements show in addition rich features inside the superconducting gap which can be attribute to thermally excited quasiparticles. More detailed experimental investigations and theoretical calculations are in progress to understand the experimental findings.