Ab Initio Analysis of a Quantum Dot Induced by a Local External Potential in a Semiconducting Carbon Nanotube

Using the density functional theory we study the influence of external charge probes on the electronic structure of semiconducting carbon nanotubes in the vicinity of the Fermi level. We show that the spatially limited potential due to the probe can create localized electronic states in the energy gap and at the edges of the conductance band. By filling these localized states with additional electrons one obtains a quantum dot, which can be tuned by modifying the properties of the external charge probe. We analyze dependence of the electronic structure of the dot on the spatial extension of the potential as well as on the nanotube radius.