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PGI-1 Talk: Dr. Alexander Mook

Chern Insulator of Magnons: Skyrmions, Interactions, and Second-Order Topology

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25 Nov 2020 11:30
venue
BigBlueButton

Univ of Basel, Switzerland

Abstract:

Condensed matter systems admit topological collective excitations above a trivial ground state, an example being Chern insulators formed by Dirac bosons with a gap at finite energies. However, in contrast to electrons, there is no particle-number conservation law for collective excitations. This gives rise to particle number-nonconserving many-body interactions whose influence on single-particle topology is an open issue of fundamental interest in the field of topological quantum materials.

Herein, I concentrate on magnons that are the elementary spin excitations of ferromagnets. A ferromagnet with Chern-insulating behavior of magnons exhibits a magnonic spectral gap hosting topologically protected chiral edge modes that unidirectionally revolve the sample. Since these chiral edge magnons may serve as directed information highways in next-generation technologies, a fundamental understanding of their formation and stability is at the very core of the topological magnonics paradigm.

I present topological magnons in three different setups: (i) skyrmion crystals, (ii) saturated chiral magnets, and (iii) stacks of honeycomb-lattice van der Waals magnets. These setups respectively serve as platforms to study (i) quantum damping due to spontaneous quasiparticle decay, (ii) interaction-stabilized topological gaps in the magnon spectrum, and (iii) second-order topology in three-dimensional samples that admit chiral states along their hinges, where facets intersect.

Contact

Prof. Dr. Stefan Blügel
Phone: +49 2461 61-4249
Fax: +49 2461 61-2850
email: s.bluegel@fz-juelich.de