Hi, my name is Börge and I am a postdoc in the group of Prof. Ingrid Mertig in Halle, Germany. I am a theoretical physicist working in the field of condensed matter physics with a special focus on magnetic systems. For the last four years, I have been working on skyrmions and related magnetic whirls. I found several alternative magnetic quasiparticles whose utility goes beyond that of conventional magnetic skyrmions, as will be presented below. If you want to get in contact, please feel free to write me an email

- Stability of magnetic textures
- Their current-driven motion
- Hall effects (OHE, AHE, THE)
- Spintronic devices
- Spin-orbitronics
- Spin-charge interconversion
- Magnetoelectricity
- Topological matter
- Mn
_{3}X, Heuslers, 2Degs

- Analytical models
- Tight-binding models
- Topological invariants
- Berry theory
- Micromagnetic simulations
- Thiele equation
- Monte-Carlo simulations
- Landauer-Büttiker simulations

- Jan 2020: PhD Summa cum laude
- (MPI Halle, Ingrid Mertig)
- Sep 2016: M. Sc. Physics
- (MLU Halle, Ingrid Mertig)
- Sep 2014: B. Sc. Physics
- (MLU Halle, Jamal Berakdar)

- Organization of group seminar
- Supervizing PhD, Ma & Ba students
- Former student speaker IMPRS Halle
- Enjoying collaborations
- Invited talks (e.g. at MMM, JEMS)

A magnetic skyrmion consists of non-collinear magnetic moments: the colored arrows in the figure above. It is topologically non-trivial,
since it cannot be continuously transformed into a ferromagnetic state. This property, characterized by its integer topological charge
Q = 1, gives
it an enourmous stability which appears to be favorable for data storage applications. In fact, skyrmions can be generated,
deleted, driven by currents and read by their unique Hall signature. Therefore, they can be considered the carriers of information
in racetrack storage devices where the presence and absence of a skyrmion at predefined positions in a magnetic stripe corresponds to
bits of 0 and 1.

Topological Hall effect
Skyrmion Hall effect

My main research focus is on circumventing the short-comings of conventional magnetic skyrmions:

- Skyrmions do not move parallel to the driving currents but instead experience the skyrmion Hall effect that pushes them towards the racetrack edge.
- Bit sequences, corresponding to present and absent skyrmions, may not be stable because skyrmions interact with each other and experience thermal diffusion.

Both problems are critical as they will lead to a malfunction of the data storage due to a
loss or change of information.

(1) The transverse motion, identified as the skyrmion Hall effect, can be surpressed by using alternative magnetic objects.
This includes objects with a vanishing topological charge, like the antiferromagnetic (AFM) skyrmion, but also objects with
a broken rotational symmetry, like bimerons or antiskyrmions.

(2) To nullify the detrimental effect of irregular
distances between the bits, one could represent the bits by two topologically distinct objects.
We have shown that this is possible due to the coexistence of skyrmions and antiskyrmions in Heusler materials.

- 25 Publications, 18 as (shared) first author
- Experimental and theoretical collaborations
- Nature Mat., Nature Commun. & Science Adv.
- Invited review paper in Physics Reports

with Oleg Tretiakov

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, the skyrmion analogues
in different magnetic surroundings or
three-dimensional generalizations. We classify the alternative
magnetic quasiparticles and present the most relevant and auspicious advantages of this
emerging field.

Physics Reports (2021)

with Stuart Parkin's group

In this colaboration with experimentalists,
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.
The observed coexistence of two topologically distinct nano-objects allows
to suggest an advanced version of a racetrack storage device.

Nature Communications (2020)

Science Advances (2020)

with Manuel Bibes' group & others

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 topological properties.
Our fit, as well as the calculations of the Edelstein effect allow to qualitatively explain
the enormously large spin-charge interconversion that was measured experimentally.

Nature Materials (2019)