Electric field-driven topological phase switching and skyrmion lattice metastability in magnetoelectric Cu$_{2}$OSeO$_{3}$

TL;DR

This study demonstrates electric field-driven switching between skyrmion and non-topological phases in an insulating magnet, revealing metastable skyrmion states and potential for low-energy topological memory devices.

Contribution

It provides direct neutron scattering evidence of electric field-induced topological phase switching and metastable skyrmion states in Cu$_{2}$OSeO$_{3}$, an insulating magnet.

Findings

Electric fields can switch skyrmion and cone phases in Cu$_{2}$OSeO$_{3}$.

Metastable skyrmion states exist over a broad temperature range.

Metastable skyrmions have hour-scale lifetimes at lower temperatures.

Abstract

Due to their topological protection and nanometric size, magnetic skyrmions are anticipated to form components of new high-density memory technologies. In metallic systems skyrmion manipulation is achieved easily under a low density electric current flow, although the inevitable thermal dissipation ultimately limits the energy efficacy of potential applications. On the other hand, a near dissipation-free skyrmion and skyrmion phase manipulation is expected by using electric \emph{fields}, thus meeting better the demands of an energy-conscious society. In this work on an insulating chiral magnet Cu$_{2}$OSeO$_{3}$ with magnetoelectric coupling, we use neutron scattering to demonstrate directly i) the creation of metastable skyrmion states over an extended range in magnetic field and temperature, and ii) the in-situ electric field-driven switching between topologically distinct phases; the skyrmion phase and a competing non-topological cone phase. For our accessible electric field range, the phase switching is achieved in a high temperature regime, and the remnant (E=0) metastable skyrmion state is thermally volatile with an exponential lifetime on hour timescales. Nevertheless, by taking advantage of the demonstrably longer-lived metastable skyrmion states at lower temperatures, a truly non-volatile and near dissipation-free topological phase change memory function is promised in magnetoelectric chiral magnets.