Effect of van-Hove singularities in single-walled carbon nanotube leads on transport through double quantum dot system

TL;DR

This study investigates how van-Hove singularities in carbon nanotube leads influence the conductance of a double quantum dot system, revealing significant effects on conductance peaks and their suppression based on energy level alignment.

Contribution

It provides a detailed analysis of the impact of van-Hove singularities on quantum dot conductance using Non-equilibrium Green function formalism.

Findings

Conductance peaks are significantly affected when the chemical potential aligns with van-Hove singularities.

Suppression of alternate conductance peaks depends on energy level positions and their separation.

Density of states in nanotube leads plays a crucial role in transport properties.

Abstract

The double quantum dot system with single-walled metallic armchair carbon nanotube leads has been studied using Non-equilibrium Green function in the Keldysh formalism. The effect of relative spacing between the energy levels of the dots, interdot tunneling matrix-element, interdot Coulomb interaction and van-Hove singularities in density of states characteristics of quasi-one-dimensional carbon nanotube leads on the conductance of the double quantum dot system has been studied. The conductance and dot occupancies are calculated at finite temperature. It is observed that the density of states of the carbon nanotube leads play a significant role in determining the conductance profile. In particular, whenever the chemical potential of the isolated double quantum dot system is aligned with the position of a van-Hove singularity in the density of states of armchair carbon nanotube leads, the height of the corresponding conductance peak falls considerably. It is further observed that the suppression in the heights of the alternate peaks depends on the relative positions of the energy levels of the dots and their magnitude of separation.