Competitive helical bands and highly efficient diode effect in F/S/TI/S/F hybrid structures

TL;DR

This paper proposes a mesoscopic superconducting diode device using ferromagnetic topological insulators, demonstrating controllable polarity and high efficiency through magnetization tuning of superconducting islands.

Contribution

It introduces a novel device design with two superconducting islands on a topological insulator, enabling controllable and highly efficient superconducting diode effects.

Findings

Diode efficiency sign controlled by magnetization tuning.

Significant increase in diode efficiency due to competing supercurrents.

Utilizes helical bands and topological surface states for enhanced performance.

Abstract

The diode effect in superconducting materials has been actively investigated in recent years. Plenty of different devices have been proposed as a platform to observe the superconducting diode effect. In this work we discuss the possibility of a highly efficient superconducting diode design with controllable polarity. We propose the mesoscopic device that consists of two separated superconducting islands with proximity induced ferromagnetism deposited on top of the three-dimensional topological insulator. Using the quasiclassical formalism of the Usadel equations we demonstrate that the sign of the diode efficiency can be controlled by magnetization tuning of a single superconducting island. Moreover, we show that the diode efficiency can be substantially increased in such device. We argue that the dramatic increase of the diode efficiency is due to competing contribution of the two superconducting islands to the supercurrent with single helical bands linked through the topological insulator surface.