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

Abstract

The T-shaped double quantum dot system with single-walled metallic armchair carbon nanotube leads has been studied using Green functions obtained by the equation of motion method. 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 temperatures. The density of states of the carbon nanotube leads is observed to 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.