Double Quantum Dots in Carbon Nanotubes
Abstract
We study the few-electron eigenspectrum of a carbon-nanotube double quantum dot with spin-orbit coupling. Exact calculation are combined with a simple model to provide an intuitive and accurate description of single-particle and interaction effects. For symmetric dots and weak magnetic fields, the two-electron ground state is antisymmetric in the spin-valley degree of freedom and is not a pure spin-singlet state. When double occupation of one dot is favored by increasing the detuning between the dots, the Coulomb interaction causes strong correlation effects realized by higher orbital-level mixing. Changes in the double-dot configuration affect the relative strength of the electron-electron interactions and can lead to different ground state transitions. In particular, they can favor a ferromagnetic ground state both in spin and valley degrees of freedom. The strong suppression of the energy gap to a ferromagnetic state can cause the disappearance of the Pauli blockade in transport experiments and thereby also limit the stability of spin-qubits in double dots based quantum information proposal. Our analysis is generalized to an array of coupled dots which is expected to exhibit rich many-body behavior.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 02, 2010
- Accession Number
- ADA534159
Entities
People
- A. M. Rey
- B. Wunsch
- E. Demler
- J. Von Stecher
- M. Lukin
Organizations
- University of Colorado Boulder