The Josephson diode effect in supercurrent interferometers

TL;DR

This paper proposes a new class of Josephson diodes based on supercurrent interferometers with mesoscopic junctions, which are electrically tunable, do not require spin-orbit coupling, and show significant non-reciprocal supercurrent effects.

Contribution

It introduces a novel Josephson diode design using supercurrent interferometers that are tunable and do not depend on Zeeman splitting or spin-orbit coupling.

Findings

Achieves up to 40% efficiency with simple two-junction design.

Efficiency can be increased by concatenating multiple interferometer loops.

Demonstrates non-reciprocal supercurrent behavior with magnetic flux control.

Abstract

A Josephson diode is a non-reciprocal circuit element that supports a larger dissipationless supercurrent in one direction than in the other. In this work, we propose and theoretically study a class of Josephson diodes based on supercurrent interferometers containing mesoscopic Josephson junctions, such as point contacts or quantum dots, which are not diodes themselves but possess non-sinusoidal current-phase relations. We show that such Josephson diodes have several important advantages, like being electrically tunable and requiring neither Zeeman splitting nor spin-orbit coupling, only time-reversal breaking by a magnetic flux. We also show that our diodes have a characteristic AC response, revealed by the Shapiro steps. Even the simplest realization of our Josephson diode paradigm that relies on only two junctions can achieve efficiencies of up to $\sim40\%$ and, interestingly, far greater efficiencies are achievable by concatenating multiple interferometer loops.