Metallic Zigzag Carbon Nanotubes Research Articles

Dynamical symmetry enlargement in metallic zigzag carbon nanotubes

We revisit correlation effects in doped metallic zigzag carbon nanotubes by using both the one-loop renormalization group and nonperturbative bosonization techniques. Note that, if a nanotube is placed near a conducting plate, the long-range Coulomb interactions are screened and the resulting short-range interactions can be modeled by on-site and nearest-neighbor repulsive interactions $U$, $V$, and ${V}_{\ensuremath{\perp}}$, respectively. Using both analytic and numeric means, we determine the phase diagram of the ground states. For $U∕tl0.5$ ($t$ is the hopping strength), dynamical symmetry enlargement occurs and the low-energy excitations are described by the SO(6) Gross-Neveu model. However, for realistic material parameters $U∕t\ensuremath{\sim}O(1)$, the charge sector decouples but there remains an enlarged SO(4) symmetry in the spin sector.

Transport through the intertube links between two parallel carbon nanotubes

Quantum transport through a junction between two metallic zigzag carbon nanotubes connected by intertube links has been studied within the tight-binding method and Landauer formula. It is found that the conductance oscillates with both the coupling strength and length. The close relation between conductance oscillations and the corresponding local densities of states is clearly shown. It indicates that the size and coupling strength effects of a nanojunction on the conductance will be important for the design of nanodevices in the future.

Oscillator Strength of Metallic Carbon Nanotubes

Based on the tight binding method with hopping integral between the nearest-neighbor atoms, an oscillator strength $\int_0^{\infty} \d \omega {\rm Re} \sigma (\omega)$ is discussed for armchair and metallic zigzag carbon nanotubes. The formulae of the oscillator strength are derived for both types of nanotubes and are compared with the result obtained by a linear chain model. In addition, the doping dependence is investigated in the absence of Coulomb interaction. It is shown that the oscillator strength of each carbon nanotube shows qualitatively the same doping dependence, but the fine structure is different due to it's own peculiar band structure. Some relations independent of the radius of the tube are derived, and a useful formula for determining the amount of doping is proposed.