Electronic and transport properties of carbon nanotube peapods

We theoretically studied the electronic and electrical properties of metallic and semiconducting nanotube peapods with encapsulated ${\mathrm{C}}_{60}$ $\left({\mathrm{C}}_{60}@\mathrm{CNT}\right)$ as a function of the carbon nanotube (CNT) diameter. For exothermic peapods (the CNT diameter>11.8 Å), only minor changes, ascribed to a small structural deformation of the nanotube walls, were observed. These include a small electron charge transfer (less than 0.10 electron) from the CNT to the ${\mathrm{C}}_{60}$ molecules and a poor mixing of the ${\mathrm{C}}_{60}$ orbitals with those of the CNT. Decreasing the diameter of the nanotube leads to a modest increase of the charge density located between the ${\mathrm{C}}_{60}’\mathrm{s}.$ More significant changes are obtained for endothermic peapods (CNT diameter<11.8 Å). We observe a large electron charge transfer from ${\mathrm{C}}_{60}$ to the tube, and a drastic change in electron transport characteristics and electronic structure. These results are discussed in terms of $\pi -\pi$ interaction and ${\mathrm{C}}_{60}$ symmetry breaking.