# Dresden 2017 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 53: Focus Session: Topology meets Magnetism

### MA 53.4: Hauptvortrag

### Donnerstag, 23. März 2017, 16:45–17:15, HSZ 01

**Magnon companion pieces to electronic topological materials** — •Alexander Mook^{1}, Jürgen Henk^{2}, and Ingrid Mertig^{1,2} — ^{1}Max-Planck-Institut für Mikrostrukturphysik, Halle, Deutschland — ^{2}Martin-Luther-Universität Halle-Wittenberg, Halle, Deutschland

Topology has conquered the field of condensed matter physics with the discovery of the quantum Hall effect. Since then the zoo of topological materials is steadily increasing. In this talk, I demonstrate how to realize different topological phases with magnons: the magnon pendants to topological insulators as well as Weyl and nodal-line semimetals are presented.

Magnon bulk spectra are characterized by topological invariants, dictating special surface properties. For instance, the bulk bands of topological magnon insulators carry nonzero Chern numbers, causing topological magnon edge states that unidirectionally revolve the sample. Magnon Weyl semimetals possess zero-dimensional band degeneracies acting as source and sink of Berry curvature; at their surface they feature "magnon arcs" connecting the surface projections of Weyl points. Magnon nodal-line semimetals exhibit one-dimensional band degeneracies, i.e., closed loops in reciprocal space. Surface projections of these nodal lines host "drumhead" surface states whose details depend strongly on the surface termination.

I discuss possible material candidates and experiments for the identification of these novel states of matter.