Anomalous crossed Andreev reflection in mesoscopic superconducting ring hosting Majorana fermions

TL;DR

This paper explores how Majorana fermions influence electron transport in a mesoscopic superconducting ring, revealing distinct Andreev reflection mechanisms and flux-dependent effects that can serve as signatures for Majorana states.

Contribution

It uncovers the topologically distinct transport mechanisms in NS-TS junctions and demonstrates flux-dependent signatures of Majorana fermions in a ring geometry.

Findings

Perfect crossed Andreev reflection occurs in short NS regions.

Perfect normal Andreev reflection occurs in short TS regions.

Flux dependence of CAR can be used to detect Majorana fermions.

Abstract

We investigate the Majorana physics and its effect on the electron transport in the non-topological superconductor(NS)-topological superconductor(TS) double junctions of a ring geometry. We find that, depending on the ratio between the lengths of two topologically different regions and the localization lengths of the Majorana fermions formed between them, two completely different transport mechanisms are working: perfect crossed Andreev reflection (CAR) for the short NS region and perfect normal Andreev reflection for the short TS region. The difference is explained in terms of the topologically distinct properties of subgap states in the NS-TS double junction system, which have not been revealed so far. The exotic dependence of the CAR process on the magnetic flux threading the ring is uncovered and can be used to detect the Majorana fermions.