Josephson Transport across T-shaped and Series-Configured Double Quantum Dots System at Infinite-U Limit

TL;DR

This theoretical study examines how Josephson current and Andreev Bound States in double quantum dot systems are affected by configuration, interdot tunneling, and energy levels, revealing interference effects and current suppression or enhancement.

Contribution

It introduces a detailed analysis of Josephson transport in T-shaped and series-configured double quantum dots at infinite-U limit using Slave Boson mean field approximation, highlighting configuration-dependent behaviors.

Findings

Interference destroys transport in T-shaped configuration.

Josephson current shows discontinuities at specific phase differences.

Current magnitude varies with interdot tunneling and energy levels.

Abstract

The charge transport has been analyzed theoretically across a T-shaped and series-configured double quantum dots Josephson junction by implementing the Slave Boson mean field approximation at an infinite-U limit. It has been shown that Andreev Bound states (ABS) and Josephson current can be tuned by varying the interdot tunneling (t) and quantum dots energy level. For the T-shape configuration of the quantum dots, an extra path is available for the transport of electrons which causes the interference destruction between two paths. For decoupled quantum dots with $\epsilon_{d1}=\epsilon_{d2}=0$, the energy of ABS crosses at $\omega=0$ and Josephson current shows a discontinuity at $\phi=\pm \pi$. On the other hand, for coupled quantum dots the lower and upper ABS has a finite spacing, the Josephson current exhibits sinusoidal nature and its magnitude suppresses with increasing interdot tunneling strength. While in the series configuration, with increment in t, Josephson current increases and shows a discontinuity at $\phi=\pm \pi$, once the system gets resonant tunneling for $t=0.5\Gamma$ with $\epsilon_{d1}=\epsilon_{d2}=0.5\Gamma$. Further, we also analyze the nature of the energy of ABS and Josephson current with the quantum dots energy level in both configurations.