Observation of Fano-Resonances in Single-Wall Carbon Nanotubes

TL;DR

This paper reports the observation of Fano resonances in the electrical conductance of single-wall carbon nanotubes, revealing quantum interference effects at high conductance regimes and transitions from quantum dot to weak link behavior.

Contribution

It provides experimental evidence of Fano resonances in metallic carbon nanotubes and discusses their origin through modeling, expanding understanding of quantum interference in nanotube conductance.

Findings

Observation of Fano resonances superimposed on conductance background

Transition from quantum dot to weak link regime with broadened levels

Conductance reaching up to 4e^2/h in high transparency regime

Abstract

We have explored the low-temperature linear and non-linear electrical conductance $G$ of metallic carbon nanotubes (CNTs), which were grown by the chemical-vapor deposition method. The high transparency of the contacts allows to study these two-terminal devices in the high conductance regime. We observe the expected four-fold shell pattern together with Kondo physics at intermediate transparency {$G\alt 2e^2/h$} and a transition to the open regime in which the maximum conductance is doubled and bound by $G_{max}=4e^2/h$. In the high-$G$ regime, at the transition from a quantum dot to a weak link, the CNT levels are strongly broadened. Nonetheless, sharp resonances appear superimposed on the background which varies slowly with gate voltage. The resonances are identified by their lineshape as Fano resonances. The origin of Fano resonances is discussed along the modelling.