Spiral magnetic order and topological superconductivity in a chain of magnetic adatoms on a two-dimensional superconductor

TL;DR

This paper investigates the emergence of topological superconductivity and spiral magnetic order in a 1D chain of magnetic adatoms on a 2D superconductor, revealing a self-organized topological phase stabilized by magnetic interactions.

Contribution

It demonstrates the existence of a self-organized topologically non-trivial superconducting phase in a magnetic adatom chain on a 2D superconductor, considering various exchange interactions and robustness factors.

Findings

Identification of a self-organized topological superconducting phase.

Robustness of the topological phase against local suppression and spin-orbit coupling.

Enlargement of spiral order region due to direct ferromagnetic exchange.

Abstract

We study the magnetic and electronic phases of a 1D magnetic adatom chain on a 2D superconductor. In particular, we confirm the existence of a `self-organized' 1D topologically non-trivial superconducting phase within the set of subgap Yu-Shiba-Rusinov (YSR) states formed along the magnetic chain. This phase is stabilized by incommensurate spiral correlations within the magnetic chain that arise from the competition between short-range ferromagnetic and long-range antiferromagnetic electron-induced exchange interactions, similar to a recent study for a 3D superconductor [M. Schecter et al. Phys. Rev. B 93, 140503(R) 2016]. The exchange interaction along diagonal directions are also considered and found to display behavior similar to a 1D substrate when close to half filling. We show that the topological phase diagram is robust against local superconducting order parameter suppression and weak substrate spin-orbit coupling. Lastly, we study the effect of a direct ferromagnetic exchange coupling between the adatoms, and find the region of spiral order in the phase diagram to be significantly enlarged in a wide range of the direct exchange coupling.