Manipulation of Cooper pair entanglement in hybrid topological Josephson junctions

TL;DR

This paper explores how gate voltage and magnetic flux can control the entanglement and supercurrent in a topological insulator-based Josephson junction, revealing simple relations between external controls and entanglement symmetry.

Contribution

It demonstrates the manipulation of non-local Cooper pair entanglement in a hybrid topological Josephson junction using external fields, linking current-phase behavior to entanglement symmetry changes.

Findings

Gate voltage controls entanglement symmetry of Cooper pairs.

External fields modify the current-phase relationship.

Critical current reflects entanglement symmetry changes.

Abstract

In this work we investigate the supercurrent in a hybrid topological Josephson junction consisting of two planes of topological insulator (TI) in a specific configuration, which allows both local (LAR) and crossed (CAR) Andreev processes at the interfaces with two conventional s-wave superconductors. We describe the effects of gate voltage and magnetic flux controls applied to the edge states of each TI. In particular, we demonstrate that the voltage gating allows the manipulation of the entaglement symmetry of non-local Cooper pairs associated to the CAR process. We establish a connection between the Josephson current-phase relationship of the system and the action of the two external fields, finding that they selectively modify the LAR or the CAR contributions. Remarkably, we find that the critical current of the junction takes a very simple form which reflects the change in the symmetry occurred to the entangled state and allows to determine the microscopic parameters of the junction.