Fano Resonance and Orbital Filtering in Multiply Connected Carbon Nanotubes

Abstract

We investigate the electron transport in multiply connected metallic carbon nanotubes within the Landauer-Büttiker formalism. Quasibound states coupled to the incident ${\pi }^{\ast }$ states give rise to energy levels of different widths depending on the coupling strength. In particular, donorlike states originating from heptagonal rings are found to give a very narrow level. Interference between broad and narrow levels produces Fano-type resonant backscattering as well as resonant tunneling. Over a significantly wide energy range, almost perfect suppression of the conduction of ${\pi }^{\ast }$ electrons occurs, which may be regarded as filtering of particular electrons ($\pi$-pass filter).