Double Quantum Dots in Carbon Nanotubes

Abstract

We study the two-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 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.

14 pages, 11 pages and 1 table. Typos in text and Figs.4 and 6 corrected

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Cited by in corpus (11)

• Quantum transport in carbon nanotubes
• Valley-spin blockade and spin resonance in carbon nanotubes
• Observation and Spectroscopy of a Two-Electron Wigner Molecule in an Ultra-Clean Carbon Nanotube
• Spin-Orbit Effects in Carbon-Nanotube Double Quantum Dots
• Inter-valley scattering induced by Coulomb interaction and disorder in carbon-nanotube quantum dots
• Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: Disordered Case
• Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: The Clean Limit
• Shape-sensitive Pauli blockade in a bent carbon nanotube
• Current hot spot in the spin-valley blockade in carbon nanotubes
• Two-electron n-p double quantum dots in carbon nanotubes
• Electronic structure of (1e,1h) states of carbon nanotube quantum dots