Modulation of electric field on low-frequency plasmons of carbon nanotubes

The electric-field-dependent plasmons of armchair and zigzag carbon nanotubes (ACNTs and ZCNTs) are calculated by the p(z)-orbital tight-binding model including curvature effect and random-phase-approximation. As electric field increases, ZCNTs undergo a zero-gap transition, whereas ACNTs remain metallic. Band structures of CNTs in electric field can exhibit many local minima and maxima leading to more transition channels. The position and amplitude of the peak-dip structures in the dielectric functions have strong dependence on field strength and nanotube?s geometry. For ACNTs and narrow-gap ZCNTs, plasmon frequency at zero field increases with increasing transferred momentum, but plasmon peak is enhanced and then reduced. With increasing field strength, plasmon frequency is lowered and the critical momentum causing a vanish of plasmon becomes smaller. Moreover, temperature provides more electronic excitation states leading to a higher plasmon frequency. There is no plasmon at zero field for moderate-gap ZCNTs, but it can be induced by applying electric field. With increasing temperature, low-frequency plasmon with THz could be further enhanced.

Automated summary

The study investigates the electric-field-dependent plasmons of armchair and zigzag carbon nanotubes, revealing the zero-gap transition in zigzag nanotubes under increasing electric field. The band structures of carbon nanotubes in electric field display multiple local minima and maxima, leading to various transition channels. The position and amplitude of peak-dip structures in the dielectric functions show strong dependence on field strength and nanotube geometry.