Coulomb versus spin-orbit interaction in few-electron carbon-nanotube quantum dots

Abstract

Few-electron states in carbon-nanotube quantum dots are studied by means of the configuration-interaction method. The peculiar non-interacting feature of the tunneling spectrum for two electrons, recently measured by Kuemmeth et al. [Nature 452, 448 (2008)], is explained by the splitting of a low-lying isospin multiplet due to spin-orbit interaction. Nevertheless, the strongly-interacting ground state forms a `Wigner molecule' made of electrons localized in space. Signatures of the electron molecule may be seen in tunneling spectra by varying the tunable dot confinement potential.

RevTeX 4.0, 4 pages, 4 postscript figures. New Fig. 4 on two-electron wave functions was added, and more insight was given on the Wigner molecule state. A mechanical error affecting the value of the dielectric constant was corrected