Electron-state control of carbon nanotubes by space and encapsulated fullerenes

We report total-energy electronic structure calculations that provide energetics of encapsulation of various fullerenes in carbon nanotubes and electronic structures of resulting carbon peapods. We find that the electron states of the peapods depend on the space in the nanotubes and that they reflect electron states of the encapsulated fullerenes. The deep energy position of the lowest unoccupied state of fullerenes as well as hybridization between $\ensuremath{\pi}$ states of the fullerenes and the nearly free-electron states of the nanotubes causes a multicarrier character in the peapods.