Anomalous field‐effect characteristics in double‐wall carbon nanotubes due to proximity effect

The anomalous field‐effect characteristic (FEC) in so‐called semiconductor‐metal (S‐M) double‐wall carbon nanotubes (DWCNTs) is explained by proximity effect. By using a two‐band tight‐binding model on a ladder of two legs, it is demonstrated that the proximity effect can convert a semiconducting shell into a weak metal. The gate voltage dependence of the metallicity corresponds to the anomalous FEC.