Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 16: Transport: Quantum Dots, Wires, Point Contacts 2 (jointly with HL)
TT 16.8: Vortrag
Montag, 11. März 2013, 17:00–17:15, H18
Spin-dependent coupling to vibrations in suspended carbon nanotube quantum dots — •Hernán L. Calvo1,2, Julian Bohle1,2,3, Christoph Stampfer2,3,4, and Maarten R. Wegewijs1,2,3 — 1Institut für Theorie der Statistischen Physik, RWTH Aachen University, Germany — 2JARA - Fundamentals of Future Information Technology — 3Peter Grünberg Institut, Forschungszentrum Jülich, Germany — 4II. Institute of Physics B, RWTH Aachen University, Germany
Recent transport experiments in a semi-suspended carbon nanotube (CNT) quantum dot have shown an electron-vibration coupling that is markedly different for spin singlet and triplet states. In this talk, we show that such an apparent spin-vibration coupling can be understood in terms of a coupling of the electronic valley degree of freedom of the CNT to the observed longitudinal vibration. Strikingly, this Peierls-type coupling in the valley space leads to Franck-Condon sidebands that mostly develop for the triplet excited state. A vibrational modulation of the exchange interaction on the CNT is shown to result in a similar, but weaker effect. The effect can be understood qualitatively from polaronic shifts obtained in the Born-Oppenheimer approximation. In the regimes of interest, however, this approximation breaks down and we present transport calculations accounting for the full pseudo-Jahn-Teller mixing of the vibronic states that show satisfactory agreement with the experiment.