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

## TL;DR

This paper proposes a new design for a superconducting diode using a hybrid structure with controllable polarity and high efficiency.

## Contribution

A novel mesoscopic device with controllable diode polarity and enhanced efficiency is proposed using topological insulators and superconducting islands.

## Key findings

- Diode efficiency sign can be controlled by magnetization tuning of a single superconducting island.
- Competing helical bands in the topological insulator significantly increase diode efficiency.
- The proposed device offers a highly efficient superconducting diode effect.

## 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 a mesoscopic device that consists of two separated superconducting islands with proximity-induced ferromagnetism deposited on top of a 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 a device. We argue that the dramatic increase of the diode efficiency is due to competing contributions of the two superconducting islands to the supercurrent with single helical bands linked through the topological insulator surface.