# Dresden 2020 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 17: Skyrmions (jointly with MA, O) (joint session TT/MA)

### MA 17.2: Vortrag

### Montag, 16. März 2020, 16:30–16:45, HSZ 304

**Quantum skyrmion state** — •Evgeny A. Stepanov^{1}, Mikhail I. Katsnelson^{2}, and Vladimir V. Mazurenko^{3} — ^{1}Institute of Theoretical Physics, University of Hamburg, Germany — ^{2}Radboud University, Institute for Molecules and Materials, Nijmegen, Netherlands — ^{3}Theoretical Physics and Applied Mathematics Department, Ural Federal University, Ekaterinburg, Russia

Skyrmions in physics of magnetism appear as classical spin structures that are formed in the systems as the result of a competition between different magnetic interactions. Such nontrivial magnetic textures can be observed in materials with the use of a spin-polarized scanning tunneling and Lorenz microscopy, or in X-ray and neutron scattering experiments. Theoretically, a skyrmion state can be described by solving a classical spin lattice problem or a corresponding continuous micromagnetic model. Here, we find that the classical skyrmion can be considered as a particular projection of a more general quantum skyrmion state. To perform a complete characterization of this novel state, we introduce a quantum analog for a classical skyrmion number that can be calculated as a scalar triple product of spin operators. We show that this quantity allows for a clear distinction of the quantum skyrmion state, which is characterized by a nontrivial correlation of spins in all three space directions, from other more simple spin orderings. On a basis of an exact numerical solution for supercells with up to 25 spins we demonstrate that the quantum skyrmion state can be obtained for a much broader range of magnetic fields than the corresponding classical skyrmion solution of the problem.