How to reveal metastable skyrmionic spin structures by spin-polarized scanning tunneling microscopy

TL;DR

This paper predicts metastable skyrmionic spin structures in ultra-thin transition-metal films and demonstrates how they can be identified using spin-polarized scanning tunneling microscopy (SP-STM) with specific contrast patterns.

Contribution

It introduces a method to detect and distinguish metastable skyrmions and antiskyrmions in surface films via SP-STM contrast analysis without full magnetization component knowledge.

Findings

Skyrmions and antiskyrmions appear with characteristic SP-STM contrasts.

Contrast varies with tip magnetization orientation, enabling unambiguous identification.

Metastable skyrmionic structures can be predicted using Monte Carlo simulations based on DFT-derived parameters.

Abstract

We predict the occurrence of metastable skyrmionic spin structures such as antiskyrmions and higher-order skyrmions in ultra-thin transition-metal films at surfaces using Monte Carlo simulations based on a spin Hamiltonian parametrized from density functional theory calculations. We show that such spin structures will appear with a similar contrast in spin-polarized scanning tunneling microscopy (SP-STM) images. Both skyrmions and antiskyrmions display a circular shape for out-of-plane magnetized tips and a two-lobe butterfly contrast for in-plane tips. An unambiguous distinction can be achieved by rotating the tip magnetization direction without requiring the information of all components of the magnetization.