Field-free Josephson diode effect in interacting chiral quantum dot junctions

TL;DR

This paper demonstrates a field-free Josephson diode effect in chiral quantum dot junctions caused by electron-electron interactions, which induce effective magnetism and rectification without external magnetic fields.

Contribution

It reveals how electron interactions and chirality in quantum dot junctions lead to a spontaneous Josephson diode effect without external magnetic fields.

Findings

Rectification coefficient reaches up to 72% with moderate Coulomb interaction.

Sign-changing behavior of the rectification coefficient with interaction strength.

Field-free Josephson diode effect enabled by electron-electron interactions and chirality.

Abstract

We investigate chiral quantum dot (QD)-based Josephson junction and show the correlation-induced Josephson diode effect (JDE) in it. The presence of electron-electron interaction spontaneously creates an imbalance between up- and down-spin electrons during the non-equilibrium transport making the QD effectively magnetic. The simultaneous presence of the chirality and the interaction eventually results in the field-free JDE in our chiral QD junction. We employ the Keldysh non-equilibrium Green's function technique to study the behavior of the Josephson current (JC) and the rectification coefficient (RC) of our Josephson diode (JD). We show a sign-changing behavior of the RC with the Coulomb correlation and the lead-to-dot coupling strength and find the maximum magnitude of the RC $\sim 72\%$ for moderate interaction strength. Our proposed field-free JD based on interacting chiral QD may be a potential switching component in superconductor based devices.