Doping of ${\text{C}}_{60}$-induced electronic states in BN nanopeapods: Ab initio simulations

We report the results of ab initio simulations of the electronic properties of a chain of ${\text{C}}_{60}$ molecules encapsulated in a boron-nitride nanotube—so-called BN nanopeapod. It is demonstrated that this structure can be effectively doped by depositing potassium atoms on the external wall of the BN nanotube. The resulting material becomes a true metallic one-dimensional crystal, where the conduction states are formed solely by the fullerene chain. At the doping rate of one K atom per ${\text{C}}_{60}$ molecule, the system shows the density of states at the Fermi level considerably higher than in any of the fullerene crystals presently made. This makes the doped BN-peapod structure an interesting candidate to study a possible superconducting state.

Figure 1

(Color online) The geometry of the ${\text{C}}_{60}@{\text{K}}_3\text{BN}\left(9,9\right)$ peapod. The large circles show the K atoms absorbed on the nanotube wall. Figure 1 shows a doubled unit cell along the tube axis.

Figure 2

The calculated band structure of (a) BN(9,9) nanotube, (b) ${\text{C}}_{60}@\text{BN}\left(9,9\right)$ peapod, and (c) free-standing linear chain of ${\text{C}}_{60}$ molecules. The zero of energy scale corresponds to the valence-band maximum.

Figure 3

Calculated density of electronic states for (a) the ${\text{C}}_{60}@\text{BN}\left(9,9\right)$ peapod doped by one electron within a rigid-band model approach, [(b)–(d)] the ${\text{C}}_{60}@{\text{K}}_x\text{BN}\left(9,9\right)$ peapod doped by one, two, and three potassium atoms, respectively. The dashed line corresponds to the Fermi-level position. The inset of (b) shows the topology of electronic bands near the Fermi level for ${\text{C}}_{60}@{\text{K}}_1\text{BN}\left(9,9\right)$ peapod.

Figure 4

The band structure of ${\text{C}}_{60}@\text{BN}\left(9,9\right)$ peapod under different potassium doping. The panels (a), (b), and (c) correspond to the doping rate of 1, 2, and 3 K atoms per ${\text{C}}_{60}$ molecule, respectively. The dashed line corresponds to the Fermi-level position.

Figure 5

(Color online) Spatial distribution of the conducting electrons at the Fermi level for the ${\text{C}}_{60}@{\text{K}}_1\text{BN}\left(9,9\right)$ peapod.