Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: TR: Nanoelectronics I: Quantum Dots, Wires, Point Contacts 2
TT 33.2: Vortrag
Donnerstag, 25. März 2010, 14:15–14:30, H19
Spin-Orbit Effects in Carbon-Nanotube Double Quantum Dots — •Stephan Weiss1, Emmanuel Rashba2,3, Ferdinand Kuemmeth2, Hugh Churchill2, and Karsten Flensberg1 — 1Niels Bohr Institute & Nano-Science Center, University of Copenhagen — 2Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA — 3Center for Nanoscale Systems, Harvard University, Cambridge, Massachusetts 02138, USA
We study the spectrum of a carbon nanotube double quantum dot with one and two electrostatically confined electrons in the presence of spin-orbit and Coulomb interactions [1]. Compared to GaAs dots the spectrum exhibits a richer structure due to the valley degree of freedom in nanotubes. Starting with the envelope function approach near the graphene Dirac point, we numerically diagonalize the two particle Hamiltonian and explain its spectrum in terms of spin and orbital singlets and triplets. We also show how spin-orbit effects compete with finite exchange Coulomb interactions at weak magnetic fields. Inspired by recent experiments that measured the relaxation and dephasing times of Kramers doublets in nanotube quantum dots, we investigate the transition between (02)↔ (11)-configurations as a function of the inter-dot detuning.
[1] S. Weiss, E.I. Rashba, F. Kuemmeth, H.O.H. Churchill, and K. Flensberg, in preparation