Josephson Effect in a T-Shaped Triple-Quantum-Dot Structure: π-Junction Behavior and Two-Stage Kondo Effect

By means of the exact diagonalization approach, the interplay between the Josephson effect and the two-stage Kondo physics in a T-shaped triple-quantum-dot (TQD) junction is theoretically investigated. It is found that by adjusting the interdot couplings, the Josephson current exhibits the rich 0-pi transition behaviors. These results originate from the mutual competition and cooperation of Cooper-pair correlation and two-stage Kondo correlation in the system. Moreover, due to the occurrence of two-stage Kondo effect, the Josephson phase transition can be adjusted in a precise manner. It is believed that this work can help to understand the supercurrent phase transition in the QD-based Josephson junctions.