Linear and nonlinear transport across carbon nanotube quantum dots

TL;DR

This paper develops a low-energy theoretical framework for understanding nonlinear electron transport in finite-size, interacting single-wall carbon nanotubes, incorporating degeneracy effects and predicting periodic conductance features.

Contribution

It introduces a microscopic model combined with bosonization to analyze nonlinear transport, accounting for degeneracy and coherences, aligning with experimental observations.

Findings

Predicts four-electron periodicity in conductance peaks

Quantitative agreement with recent experimental data

Highlights the role of degeneracy and coherences in transport

Abstract

We present a low energy-theory for non-linear transport in finite-size interacting single-wall carbon nanotubes. It is based on a microscopic model for the interacting p_z electrons and successive bosonization. We consider weak coupling to the leads and derive equations of motion for the reduced density matrix. We focus on the case of large-diameter nanotubes where exchange effects can be neglected. In this situation the energy spectrum is highly degenerate. Due to the multiple degeneracy, diagonal as well as off-diagonal (coherences) elements of the density matrix contribute to the nonlinear transport. At low bias, a four-electron periodicity with a characteristic ratio between adjacent peaks is predicted. Our results are in quantitative agreement with recent experiments.