Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 37: MLT: Poster Session
TT 37.26: Poster
Donnerstag, 25. März 2010, 14:00–18:00, Poster A
Low Energy Effective Theory for Nanotubes with Spin Orbit coupling — •Stephan Weiss1, Frederik Treue1, Emmanuel Rashba2,3, 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
Spin orbit coupling in nanotubes has motivated experimental and theoretical research activities recently. Due to the interplay between curvature and atomic SO coupling, the single particle spectrum exhibits a finite gap at zero magnetic field between the two Kramers doublets. We present different approaches in order to derive the low energy effective Hamiltonian [1]. First based on symmetry arguments we derive the Hamiltonian. This settles the number of free coupling constants as well as the general form of the Hamiltonian. In a second approach, we employ a four band tight binding calculation for the π and σ bands of graphene and include curvature between the bonds and atomic spin orbit coupling in lowest order perturbation theory. We are able to give estimates for the coupling constants, based on the known tight binding parameters for plane graphene. A fully numerical approach, which involves a Hückel approximation on the overlap integrals between neighboring atoms is used to calculate the SO coupling parameter for different chiralities of nanotubes and the zero field gap for electrons and holes.
[1] S. Weiss, F. Treue, E.I. Rashba, and K. Flensberg, in preparation.