Magnonic analogs of topological insulators in two and three dimensions

Speaker: Hosho Katsura – Tokyo University

Host: Dirk Schuricht

Abstract:

Magnons (or spin waves) are collective excitations in magnets responsible for their magnetic and thermal properties. Recently, there has been a growing interest in studying magnetic systems with nontrivial magnon band topology. However, examples discussed so far have been mostly limited to systems which can be thought of as a magnonic analog of integer quantum Hall systems. In this talk, I will talk about a class of magnonic systems that are the natural counterparts of time-reversal symmetric topological insulators in two and three dimensions [1,2]. The feature of these systems is that each pair of bands related by pseudo-time-reversal symmetry carries a Z2 topological invariant. I will demonstrate that the Z2 invariant so defined characterizes the presence/absence of helical edge/surface modes. If time permits, I will touch on magnonic analogs of topological crystalline insulators [3].

[1] H. Kondo, Y. Akagi, and H. Katsura, Phys. Rev. B 99, 041110(R) (2019).
[2] H. Kondo, Y. Akagi, and H. Katsura, Phys. Rev. B 100, 144401 (2019).
[3] H. Kondo and Y. Akagi, Phys. Rev. Lett. 127, 177201 (2021).