Spin selective coupling to Majorana zero modes in mixed singlet and triplet superconducting nanowire

TL;DR

This paper theoretically explores how the relative orientation of magnetization and the d-vector in a mixed singlet-triplet superconductor nanowire influences Majorana zero modes and conductance, revealing a spin-selective coupling mechanism.

Contribution

It introduces a model showing how the orientation of ferromagnetic and superconducting vectors controls Majorana modes and conductance in a hybrid nanowire system.

Findings

Majorana zero modes appear in the topological phase with dominant triplet pairing.

Conductance switches between 4e^2/h and 2e^2/h depending on magnetization orientation.

Spin-selective coupling of Majorana modes to the lead is demonstrated.

Abstract

We theoretically investigate the transport properties of a quasi one dimensional ferromagnet-superconductor junction where the superconductor consists of mixed singlet and triplet pairings. We show that the relative orientation of the stoner field ($\bf{\tilde{h}}$) in the ferromagnetic lead and the $\bf{d}$ vector of the superconductor acts like a on-off switch for the zero bias conductance of the device. In the regime, where triplet pairing amplitude dominates over the singlet counterpart (topological phase), a pair of Majorana zero modes appear at each end of the superconducting part of the nanowire. When $\bf{\tilde{h}}$ is parallel or anti-parallel to the $\bf{d}$ vector, transport gets completely blocked due to blockage in pairing while, when $\bf{\tilde{h}}$ and $\bf{d}$ are perpendicular to each other, the zero energy two terminal differential conductance spectra exhibits sharp transition from $4e^2/h$ to $2e^2/h$ as the magnetization strength in the lead becomes larger than the chemical potential indicating the spin selective coupling of pair of Majorana zero modes to the lead.