Intrinsic and Tunable Superconducting Diode Effect in Quantum Spin Hall Systems

TL;DR

This paper theoretically demonstrates the emergence of a tunable superconducting diode effect in quantum spin Hall systems, controllable by external fields or intrinsic edge reconstruction, with potential for high-efficiency nonreciprocal superconducting devices.

Contribution

It introduces a new mechanism for the superconducting diode effect in quantum spin Hall systems, including both externally controlled and intrinsic forms, expanding understanding of nonreciprocal superconductivity.

Findings

Superconducting diode effect can be controlled by magnetic and electric fields in large quantum wells.

Intrinsic diode effect can arise from edge reconstruction without external magnetic fields.

Achieves unit efficiency in controlling the diode effect.

Abstract

Nonreciprocal dissipationless transport has long been sought for applications in superconducting technologies. Recently, it has been implemented by the so called superconducting diode effect. Such effect arises from an imbalance in critical supercurrents flowing in opposite directions. In this work, we theoretically demonstrate how the superconducting diode effect emerges in the quantum spin Hall phase when brought into full proximity with a superconductor. We explore two regimes: large and narrow quantum wells. In the former geometry, we show that the superconducting diode effect can be externally controlled using both magnetic and electric fields, achieving unit efficiency. In the latter regime, where tunneling between opposite edges may occur, we propose a mechanism for an intrinsic superconducting diode effect driven by edge reconstruction, which does not require external magnetic fields.