Eur. Phys. J. B 36, 411-418 (2003)
https://doi.org/10.1140/epjb/e2003-00360-7

Size effect of quantum conductance in single-walled carbon nanotube quantum dots

¹ Physics Department, Nanjing Normal University, Nanjing 210097, P.R. China
² Physics Department, Peking University, Beijing 100871, P.R. China

Corresponding author: ^a liuhong3@pine.njnu.edu.cn

Received: 31 May 2003
Revised: 8 August 2003
Published online: 23 December 2003

Abstract

The quantum conductance of two kinds of carbon nanotube quantum dots (CNQD) composed of (5,5) and (10,0) tubes, namely (10,0)/(5,5)/(10,0) and (5,5)/(10,0)/(5,5) with different quantum sizes, are calculated. It is shown that for (10,0)/(5,5)/(10,0) CNQD, one on-resonant peak at the Fermi energy exists only for special QD sizes, and the width of the conductance gap increases from 1.0 eV to 3.2 eV with the increase of size. The positions of peaks around the Fermi energy are obtained by the electronic structure of individual finite (5,5) tubes. We also find that the (5,5)/(10,0)/(5,5) CNQDs behave as a quantum dot, and its localized QD states are different from that of the former CNQD because of the existence of the interface states between (5,5)/(10,0) junctions. For (5,5)/(10,0)/(5,5) CNQD, there is no conductance gap with QD's size smaller than 7 layers, and the conductance peak around the interface quasilocalized state -0.26 eV disappears with QD sizes larger than 23 layers. In addition, for the (5,5)/(10,0)/(5,5) CNQD, the connection method can change the degree of electronic localization of intermediate (10,0) tube.