Ben McKeever

I am working on skyrmions in magnetic materials and in quantum Hall systems.

For my purposes, skyrmions are a type of topological soliton — localised, particle-like objects with a finite energy and an integer topological charge — that live in two dimensions of space.

In magnetic systems, skyrmions are twisted spin textures in thin slices of materials where the magnetization slowly varies. A desire is for them to unlock new possibilities for spintronics applications, skyrmionics, due to their special properties. This includes their topological stability and their favourable sensitivity to ultra-low electric currents compared to domain walls. Isolated magnetic skyrmions are now obtainable at room temperature, where they have been observed moving at high enough speeds for processing, and they may also be individually created and destroyed. This motivates us to develop and test our theoretical understanding of the dynamics of individual magnetic skyrmions.

Before skyrmions were discovered in magnetic systems they were also studied in quantum Hall (QH) systems. Here they exist as the lowest energy excitations of the quantum Hall states at integer values of the filling factor, where, due to strong Coulomb interactions, the ground state consists of fully spin-polarized itinerant electrons. The QH skyrmions therefore also hold an electric charge which is intrinsically related to their topology, and they often dominate the low-temperature properties of the so-called quantum Hall ferromagnets.

Recently I have worked on effective theories for excitations of single skyrmions in magnetic thin films.

Simulation of a large Néel-type magnetic skyrmion (left) rendered in ParaView, and skyrmion breathing mode (right) shown across a time period T.

 

 

Publications

  • B.F. McKeever, D.R. Rodrigues, D. Pinna, Ar. Abanov, J. Sinova, K. Everschor-Sitte, "Characterizing breathing dynamics of magnetic skyrmions and antiskyrmions within the Hamiltonian formalism", Phys. Rev. B 99, 054430 (2019)