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SFB1238 | Jeffrey Rau

On 17 April at 14:30 - 15:30 in Seminar Room of the Institute of Physics II

Jeffrey Rau, MPI-PKS Dresden

 

Topological magnons and the non-Hermitian topology of spontaneous magnon decay

 

Recently, magnon excitations have been explored as a potential route to

realizing analogues of the topological band structures that have become

ubiquitous in electronic systems. However, magnons are not necessarily

stable quasi-particles, with spontaneous magnon decay a generic feature

of anisotropic magnets or magnets with non-colinear order. In this talk

I will discuss two aspects of this physics: First, I will discuss how

sharp topological magnon bands can exist in spite of the presence

allowed decays, as realized in a Kitaev model in a large magnetic field.

Second, I will discuss an alternative scenario where decay in fact

drives the appearance new kinds of intrinsically non-Hermitian

topological physics. This can lead to new kinds of spectral features,

such as exceptional points and bulk "arcs" connecting them. I will

illustrate this physics through a concrete example: a honeycomb

ferromagnet with Dzyaloshinskii-Moriya exchange, comparing interacting

spin-wave calculations with an effective non-Hermitian model. Finally, I

discuss more broadly how the zoo of known topological protected magnon

band structures may serve as a nearly ideal platform for realizing

non-Hermitian physics in solid-state systems.

 

Contact Person: Ciarán Hickey