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

TL;DR

This paper investigates the effects of Coulomb and spin-orbit interactions on few-electron states in carbon-nanotube quantum dots, explaining experimental tunneling spectra and revealing electron localization phenomena.

Contribution

It provides a detailed analysis of how spin-orbit interaction influences the tunneling spectrum and ground state configuration in carbon-nanotube quantum dots, highlighting the formation of a Wigner molecule.

Findings

Splitting of isospin multiplet due to spin-orbit interaction explains non-interacting tunneling features.

Strong electron-electron interactions lead to Wigner molecule formation.

Tunneling spectra can reveal electron localization by varying confinement potential.

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.