Proposal for an on-demand source of polarized electrons into the edges of a topological insulator

TL;DR

This paper proposes a device for on-demand emission of spin-polarized electron pairs into topological insulator edges, utilizing a driven quantum dot, with potential for entanglement generation and experimental detection via noise measurements.

Contribution

It introduces a novel device design for controlled spin-polarized electron emission and demonstrates how entanglement can be generated and detected in this system.

Findings

Emission of spin-polarized electron pairs is theoretically modeled.

A new noise suppression phenomenon, $\\mathbb{Z}_2$--antibunching, is predicted.

Entanglement of emitted electrons can be demonstrated via Bell inequality violation.

Abstract

We propose a device that allows for the emission of pairs of spin-polarized electrons into the edge-states of a two dimensional topological insulator. Charge and spin emission is achieved using a periodically driven quantum dot weakly coupled to the edge states of the host topological insulator. We present calculations of the emitted time-dependent charge and spin currents of such a dynamical scatterer using the Floquet scattering matrix approach. Experimental signatures of spin-polarized two-particle emission can be found in noise measurements. Here a new form of noise suppression, named $\mathbb{Z}_2$--antibunching, is introduced. Additionally, we propose a set-up in which entanglement of the emitted electrons is generated. This entanglement is based on a post-selection procedure and becomes manifest in a violation of a Clauser-Horne-Shimony-Holt inequality.