Martin Luther University Halle-Wittenberg

Dr. Börge Göbel

Emergent electrodynamics in non-collinear spin textures

Börge Göbel (Photo:private)

Börge Göbel (Photo:private)

For the last three years, the main focus of my research has been on skyrmionics. I considered the stabilization and emergent electrodynamic effects (topological Hall effect and current-driven motion) of topologically non-trivial spin textures by conducting spin dynamics simulations and by utilizing the Berry theory approach for electronic transport phenomena. A great part of my research has been dedicated to finding and investigating alternative magnetic quasiparticles whose utility goes beyond that of conventional magnetic skyrmions. Please feel free to read our review paper   .

Research topics

  • Stabilization of skyrmions and other non-collinear spin textures
    (Monte Carlo simulations and analytical models)
  • Topological (spin) Hall effect
    (Berry theory, Kubo and Landauer-Büttiker formalism)
  • Current-induced motion of non-collinear spin texture
    (Micromagnetic simulations & effective equations of motion)
  • Magnetoelectric phenomena in non-collinear spin textures
  • Magnetoelectric effect and anomalous Hall effect in Mn3X materials
  • Quantum Hall effect in lattice models
  • Spin-to-charge conversion (Edelstein effect & spin Hall effect)
  • Analogues to electronic Hall effects for magnons
  • Spintronic devices

News

Publications

Recent invited talks

  • 12/2020 JEMS (Joint European Magnetism Symposia, Portugal).
    Elliptical Bloch skyrmion chiral twins in an antiskyrmion system
  • 11/2020 MMM (Magnetism and Magnetic Materials Conference, USA).
    Beyond skyrmions: alternative magnetic quasiparticles
  • 11/2020 Young Research Leaders Workshop (SPICE, Mainz).
    Beyond skyrmions: alternative magnetic quasiparticles

Contact

Dr. Börge Göbel

room 1.18b
Von-Seckendorff-Platz 1
06120 Halle (Saale)

phone: +49 (0) 345 55-25451
fax: +49 (0) 345 55-25446


Highlights

Beyond skyrmions: Review and perspectives of alternative magnetic quasiparticles

In this review paper, we present recent trends in the field of topological spin textures that go beyond skyrmions. The majority of these objects can be considered a combination of multiple subparticles, such as the bimeron, or the skyrmion analogues in different magnetic surroundings, such as antiferromagnetic skyrmions, as well as three-dimensional generalizations, such as hopfions. We classify the alternative magnetic quasiparticles – some of them observed experimentally, others theoretical predictions – and present the most relevant and auspicious advantages of this emerging field.

Antiskyrmions and elliptical skyrmions in Heusler materials

In this colaboration with experimentalists from the the Max Planck Institutes from Halle and Dresden, we show that Heusler materials give rise to antiskyrmions but also to elliptically deformed skyrmions.
While the antiskyrmions are stabilized by the anisotropic DMI, the skyrmions are stabilized by the dipole-dipole interaction. Consequently, they are of Bloch type and come in both chiralities.
The observed coexistence of two topologically distinct nano-objects allows to suggest an advanced version of a racetrack storage device as shown in the figure.

Giant spin-charge conversion in oxide 2D electron gas

In this experimental cooperation we present the formation of a two-dimensional electron gas at the interface of STO and Al. As shown by the tight-binding fit of the measured band structure, the system exhibits an avoided crossing leading to an enormous spin-to-charge conversion.

Antiferromagnetic skyrmions crystals and topological spin Hall effect

We present a general scheme that allows for the stabilization of antiferromagnetic skyrmions which are the most promising candidates for bits in future storage devices. Furthermore, we predict the topological spin Hall effect, which may become crucial for their experimental discovery. Up to now, antiferromagnetic skyrmions are hardly detectable due to their compensated magnetization and topological charge - they are constructed from skyrmions, living on two layers or sublattices, with mutually reversed magnetic moments.

Magnetic bimerons – Skyrmions in in-plane magnetized materials

We describe how a magnetic bimeron can be constructed mathematically by rotating all magnetic moments of a skyrmion by 90° around an in-plane axis. This leads to conclusions for their stabilization, the exhibited topological Hall effect and the current-driven motion of these quasiparticles. Most remarkably, the existence of bimerons allows to use new materials for the construction of racetrack devices. Furthermore, bimerons exhibit a purely topological Hall effect - an effect which is always superposed by the conventional and the anomalous Hall effects for skyrmionic textures.

Up