Proposal for an all-electrical measurement of crossed Andreev reflection in topological insulators

TL;DR

This paper proposes an all-electrical method to measure crossed Andreev reflection in topological insulators by exploiting spatial separation of effects in a quantum spin Hall insulator-superconductor junction, enabling clearer experimental detection.

Contribution

It introduces a novel all-electrical measurement scheme for crossed Andreev reflection in topological insulators using system geometry and spin properties.

Findings

Significant crossed Andreev reflection in narrow QSHI-SC-QSHI systems.

Spatial separation of CAR and electron cotunneling effects.

Feasibility of electrical detection in a 5-terminal or H-bar setup.

Abstract

Using a generalized wave matching method we solve the full scattering problem for quantum spin Hall insulator (QSHI) - superconductor (SC) - QSHI junctions. We find that for systems narrow enough so that the bulk states in the SC part couple both edges, the crossed Andreev reflection (CAR) is significant and the electron cotunneling (T) and CAR become spatially separated. We study the effectiveness of this separation as a function of the system geometry and the level of doping in the SC. Moreover, we show that the spatial separation of both effects allows for an all-electrical measurement of CAR and T separately in a 5-terminal setup or by using the spin selection of the quantum spin Hall effect in an H-bar structure.