Mechanisms of skyrmion collapse revealed by sub-nm maps of the transition rate

TL;DR

This study uses high-resolution microscopy and simulations to understand how magnetic skyrmions, promising for future computing technologies, collapse at the atomic level, revealing mechanisms that can be controlled to enhance their stability.

Contribution

It provides the first nanometer-scale maps of skyrmion transition rates during collapse and compares experimental results with simulations to identify collapse mechanisms under different magnetic fields.

Findings

Radial symmetric collapse at zero in-plane magnetic field.

Transition to chimera collapse at finite in-plane magnetic field.

Collapse rate can be tuned by magnetic field by up to four orders of magnitude.

Abstract

Magnetic skyrmions are key candidates for novel memory, logic, and neuromorphic computing. An essential property is their topological protection caused by the whirling spin texture as described by a robust integer winding number. However, the realization on an atomic lattice leaves a loophole for switching the winding number via concerted rotation of individual spins. Hence, understanding the unwinding microscopically is key to enhance skyrmion stability. Here, we use spin polarized scanning tunneling microscopy to probe skyrmion annihilation by individual hot electrons and obtain maps of the transition rate on the nanometer scale. By applying an in-plane magnetic field, we tune the collapse rate by up to four orders of magnitude. In comparison with first-principles based atomistic spin simulations, the experiments demonstrate a radial symmetric collapse at zero in-plane magnetic field and a transition to the recently predicted chimera collapse at finite in-plane field. Our work opens the route to design criteria for skyrmion switches and improved skyrmion stability.