Beyond Heisenberg Solids: From Multi-Spin Interactions to Novel Magnetic Particles
It became customary to study the stability, lifetime, dynamics, thermodynamics and transport properties of localized nanoscale magnetization particles such as skyrmionics by classical spin-lattice models with pairwise Heisenberg-type exchange interactions. The mapping of fermionic many-body systems onto a classical Heisenberg model is a nontrivial thing and by far not unique. In this presentation I motivate beyond Heisenberg multi-spin interactions [1]. I give examples, where these interactions play a decisive role [2]. I focus on MnGe in the B20- phase, which exhibits a three-dimensional spin-texture. We introduce a novel class of magnetic exchange interactions [3] – the topological-chiral interactions (TCI) rooted in the socalled topological orbital moment, which manifests as a result of finite scalar spin chirality in non-coplanar magnets. The long-wave length limit of the interactions relates to the highly acclaimed Faddeev model demonstrating that the interaction is an origin of 3D magnetization textures all the way down to hopfions.
[1] M. Hoffmann, S. Blügel, PRB 10, 024418 (2019).
[2] A. Krönlein, M. Schmitt, M. Hoffmann, J. Kemmer, N. Seubert, M. Vogt, J. Küspert, M. Böhme, B. Alonazi, J. Kügel, H. A. Albrithen, M. Bode, G. Bihlmayer, and S. Blügel, PRL 120, 207202 (2018).
[3] S. Grytsiuk, J.-P. Hanke, M. Hoffmann, J. Bouaziz, O. Gomonay, G. Bihlmayer, S. Lounis, Y. Mokrousov, S. Blügel, Nat. Commun. 11, 511 (2020).
Speaker Bio:
Stefan Blügel is Full Professor at the Department of Physics of the German Excellence
University RWTH Aachen and he is Institute Director of the department Quantum Theory of
Materials member of the Peter Grünberg Institute and the Institute for Advanced
Simulation.
He studied Physics at the University of Saarbrücken in Germany, at the college of William
and Mary in Virginia (US) and at the RWTH Aachen University where he finished his Master
degree in physics in 1977, his PhD in Physics in 1988 and his Habilitation in Physics in 1996.
He was postdoc between 1988 and 1990 with Professor Terakura at the Institute for Solid
State Physics at the Tokyo University in Japan.
The scientific key-interest of Stefan Blügel lies in the field of Density functional theory in
combination with magnetism, spintronics, spin-orbit related phenomena, low-dimensional
physics, 2D-materials and quantum materials. He and his group develop all-electron density
functional theory methods for these fields, in particular the Full-potential Linearized
Augmented Plane Wave open source code FLEUR and also Korringa-Kohn-Rostoker Green
function methods. He tries to develop these methods in the direction of exascale and highthroughput
computing. He is one of the discoverers of the interface Dzyaloshinskii-Moriya
Interaction.
He advised about 77 PhD students, published about 540 papers in refereed journals which
have cited about 24000 times. He received several national prizes and a Synergy Grant of
the European Research Council.
