Eur. Phys. J. B 70, 185-191 (2009)
https://doi.org/10.1140/epjb/e2009-00195-2

Controlled π-junctions in a T-shaped double quantum dot system

¹ Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing, 100083, P.R. China
² Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, 80523, USA

Corresponding author: ^a hpan@buaa.edu.cn

Received: 16 January 2009
Revised: 6 April 2009
Published online: 3 June 2009

Abstract

The π-junction transition of a T-shaped double quantum dot system is investigated theoretically by using the nonequilibrium Green's function method. It is found that the π-junction transition can occur with increasing the spin-flip strength. Furthermore, the π-junction in the system can be controlled by tuning the system parameters, such as the two quantum dot energy levels and the interdot coupling. These controlled π-junction transitions are interpreted in the picture of current-carrying density of states. When the main contributions to supercurrent is changed between the positive discrete spectrum and the negative continuous spectrum, the π-junction transitions can happen.