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

• Published in: arXiv.org 2021-07
• Main Authors: Zhu, Fengfeng, Zhang, Lichuan, Wang, Xiao, dos Santos, Flaviano José, Song, Junda, Mueller, Thomas, Schmalzl, Karin, Schmidt, Wolfgang F, Ivanov, Alexandre, Park, Jitae T, Xu, Jianhui, Ma, Jie, Lounis, Samir, Blügel, Stefan, Mokrousov, Yuriy, Su, Yixi, Brückel, Thomas
• Format: Article
• Language: English
• Subjects: Excitation; Ferromagnetism; Germanium; Inelastic scattering; Magnons; Neutron scattering; Neutrons; Silicon compounds; Spintronics; Topological insulators; Two dimensional materials
• ISSN: 2331-8422

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.