A semiconducting nanotube quantumdot: effect of the form of the confinement potential

Roy, Mervyn; Maksym, P. A.

doi:10.1002/pssc.200671595

Cited by 4 publications

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“…[1]. In this type of dot, the confinement potential is electrostatic and soft walled [1,13]. The details depend on the exact specifications of the device but, near to the centre of the NT, the potential varies quadratically with a gate voltagedependent energy zero, and we use a 1D harmonic confinement potential in our model.…”

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Semiconducting carbon nanotube quantum dots: Calculation of the interacting electron states by exact diagonalisation

Roy

Maksym

2009

Europhys. Lett.

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Abstract. -In semiconducting carbon nanotube quantum dots that contain a few interacting electrons the electron-electron correlation is always important. The states of up to 6 interacting electrons in such a dot are calculated by exact diagonalisation of a 2-band, effective mass Hamiltonian. The addition energy and the few electron density are investigated for a wide range of dots with different physical properties and, in a large proportion of these dots, the electrons are found to form Wigner molecules.Introduction. -It is now possible to form one dimensional quantum dots from high quality semiconducting carbon nanotubes [1]. Quantum dots are tunable artificial atoms that provide an ideal laboratory for exploring the physics of atoms and molecules and have many potential applications, for example in quantum computing. As dots can be used to controllably confine small numbers of charge carriers they have stimulated much interest in the quantum states of a few interacting electrons. One dimensional nanotube (NT) dots are, however, very different to the 2D semiconductor dots that have been used to study effects such as the formation of all electron (Wigner) molecules [2,3] and electronic shell filling analogous to that observed in atoms [4]. The reduced dimensionality of NT dots alters the form of the effective Coulomb interaction [5], it affects the allowed symmetries of the states [6] and the types of confinement that can be engineered.In particular, NT dots can be used to fabricate room temperature single electron transistors because of the large single particle level spacings which can be engineered [7]. They are promising candidates for spin qubits [8] and also exhibit interesting shell filling effects due to the approximately degenerate [8] K, K ′ sub-bands. This has been examined in detail in metallic NT dots [9,10] but, only recently has it been possible to accurately measure the addition energy [1] or the differential conductance [11] of semiconducting NT dots.In the Coulomb blockade [4] regime the occupancy of all types of NT dot can be controlled to the level of a single electron. Importantly, however, semiconductor NT

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Semiconducting carbon nanotube quantum dots: Calculation of the interacting electron states by exact diagonalisation

Roy

Maksym

2009

Europhys. Lett.

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“…In our dot model electrons are confined electrostatically near the tube centre and the 1D dot confinement potential is harmonic [1,2]. We can write down an effective mass theory to describe the states of such a dot and there are some new features that arise from the NT band structure.…”

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confidence: 99%