Confinement-induced Majorana modes in a nodal topological superconductor

TL;DR

This paper explores how quantum confinement can induce Majorana zero modes in a topological superconductor derived from an extended Haldane model, revealing new pathways to realize quasi-one-dimensional topological phases.

Contribution

It demonstrates that quantum confinement can stabilize Majorana zero modes in a 2D nodal topological superconductor, providing a novel mechanism for topological phase engineering.

Findings

A topological nodal superconducting phase with chiral Majorana edge modes was identified.

Quantum confinement gaps out bulk states, enabling hybridization of edge states into Majorana zero modes.

The topological phase exhibits a quantized conductance of 2 e^2/h in a normal-superconductor junction.

Abstract

We investigate the topological phase diagram of {an extension of the Haldane model with equal spin pairing superconductivity}. In two dimensions, we find a topological nodal superconducting phase, which exhibits a chiral Majorana mode propagating along the edges of nanoribbons with cylindrical boundary conditions. This phase is however unstable in a finite two-dimensional rectangular-shaped lattice, yielding corner states close to zero energy in a flake with alternating zigzag and armchair edges. When we reduce one of the dimensions, quantum confinement gaps out the bulk bands faster than the edge states. In this scenario, hybridization between the edge states can then result in Majorana zero modes. Our results hence suggest quantum confinement as a crucial ingredient in building quasi-one-dimensional topological superconducting phases out of two-dimensional nodal topological superconductors. Furthermore, we characterize the emergence of this novel topological phase by means of its topological invariant, coinciding with a quantized conductance of $2 e^2/h$ in a normal-superconducting junction.