Spin-Pairing Correlations and Spin Polarization of Majorana Bound States in Two-Dimensional Topological Insulator Systems

TL;DR

This paper investigates the spin properties and pairing correlations of Majorana bound states in two-dimensional topological insulator systems, revealing spin-triplet correlations and polarization features that aid experimental detection.

Contribution

It introduces the analysis of spin-triplet pairing and polarization in Majorana states within 2D topological insulators, highlighting their experimental signatures.

Findings

Majorana bound states exhibit three types of spin-triplet pairing correlations.

Spin polarization direction remains position independent in ferromagnetic insulators.

Equal-spin Andreev reflection resonance peaks depend on spin alignment.

Abstract

We demonstrate that zero-energy Majorana bound state, in the ferromagnetic insulator (FI)-superconductor (SC) junction formed on the edge of two-dimensional topological insulator, exhibits three types of spin-triplet pairing correlations and its spin polarization direction is position independent in ferromagnetic insulator. When an electron is injected with a spin (anti-)parallel to this direction, equal-spin Andreev reflection exhibits the widest (narrowest) resonance peak. Similar behaviour is found when the coupling between two Majorana bound states in a FI-SC-FI junction is invoked, though an additional weak spin-singlet pairing correlation is generated. These signatures can readily facilitate the experimental detection of spin-triplet correlations and spin polarization of Majorana bound states.