2010/06/30 by J. von Stecher, B. Wunsch, Bernhard Wünsch +6 · 2 citations
Engineering · Materials Science · Physics and Astronomy · #Antisymmetric relation #Carbon nanotube #Carbon nanotube quantum dot #Condensed matter physics #Coulomb #Coulomb blockade #Electron #Ferromagnetism #Graphene research and applications #Ground state #Materials science #Molecular Junctions and Nanostructures #Nanotechnology #Nanotube #Pauli exclusion principle #Physics #Quantum #Quantum and electron transport phenomena #Quantum dot #Quantum mechanics #Qubit #Spin (aerodynamics) #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevb.82.125437
published as Phys. Rev. B 82, 125437 (2010) · 14 pages, 11 pages and 1 table. Typos in text and Figs.4 and 6 corrected
arxiv created 2010/08/30 · openalex publication_date 2010/09/20 · arxiv updated 2015/05/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the two-electron eigenspectrum of a carbon-nanotube double quantum dot with spin-orbit coupling. Exact calculations 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 can cause the disappearance of the Pauli blockade in transport experiments and thereby can also limit the stability of spin qubits in quantum information proposals. Our analysis is generalized to an array of coupled dots which is expected to exhibit rich many-body behavior.