Fano Resonance and Orbital Filtering in Multiply Connected Carbon Nanotubes

TL;DR

This paper studies electron transport in complex carbon nanotubes, revealing Fano resonances and orbital filtering effects that can selectively suppress certain electron conduction pathways.

Contribution

It demonstrates how quasibound states and interference effects lead to electron filtering in multiply connected carbon nanotubes, a novel insight into nanoscale electron control.

Findings

Identification of narrow quasibound states from heptagonal rings.

Observation of Fano-type resonant backscattering.

Almost complete suppression of π* electron conduction over wide energy ranges.

Abstract

We investigate the electron transport in multiply connected metallic carbon nanotubes within the Landauer-B\"{u}ttiker formalism. Quasibound states coupled to the incident $\pi^{*}$ 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 $\pi^{*}$ electrons occurs, which may be regarded as filtering of particular electrons ($\pi$-pass filter).