Topological magnon insulators in two-dimensional van der Waals ferromagnets CrSiTe$_3$ and CrGeTe$_3$: towards intrinsic gap-tunability

Fengfeng Zhu; Lichuan Zhang; Xiao Wang; Flaviano José dos Santos; Junda Song; Thomas Mueller; Karin Schmalzl; Wolfgang F. Schmidt; Alexandre Ivanov; Jitae T. Park; Jianhui Xu; Jie Ma; Samir Lounis; Stefan Blügel; Yuriy Mokrousov; Yixi Su; Thomas Brückel

arXiv · 2107.03835

Topological magnon insulators in two-dimensional van der Waals ferromagnets CrSiTe$_3$ and CrGeTe$_3$: towards intrinsic gap-tunability

Fengfeng Zhu·Lichuan Zhang·Xiao Wang·Flaviano José dos Santos·Junda Song·Thomas Mueller·Karin Schmalzl·Wolfgang F. Schmidt·Alexandre Ivanov·Jitae T. Park·Jianhui Xu·Jie Ma·Samir Lounis·Stefan Blügel·Yuriy Mokrousov·Yixi Su·Thomas Brückel

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Abstract

The bosonic analogues of topological insulators have been proposed in numerous theoretical works, but their experimental realization is still very rare, especially for spin systems. Recently, two-dimensional (2D) honeycomb van der Waals (vdW) ferromagnets have emerged as a new platform for topological spin excitations. Here, via a comprehensive inelastic neutron scattering study and theoretical analysis of the spin-wave excitations, we report the realization of topological magnon insulators in CrXTe$_3$ (X=Si, Ge) compounds. The nontrivial nature and intrinsic tunability of the gap opening at the magnon band-crossing Dirac points are confirmed, while the emergence of the corresponding in-gap topological edge states is demonstrated theoretically. The realization of topological magnon insulators with intrinsic gap-tunability in this class of remarkable 2D materials will undoubtedly lead to new and fascinating technological applications in the domain of magnonics and topological spintronics.

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Fengfeng Zhu, Lichuan Zhang, Xiao Wang, Flaviano José dos Santos, Junda Song, Thomas Mueller, Karin Schmalzl, Wolfgang F. Schmidt, Alexandre Ivanov, Jitae T. Park, Jianhui Xu, Jie Ma, Samir Lounis, Stefan Blügel, Yuriy Mokrousov, Yixi Su, Thomas Brückel. 2021-07-08. Topological magnon insulators in two-dimensional van der Waals ferromagnets CrSiTe$_3$ and CrGeTe$_3$: towards intrinsic gap-tunability. https://arxiv.org/abs/2107.03835

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