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

TL;DR

This paper reports the experimental realization of topological magnon insulators in 2D van der Waals ferromagnets CrSiTe3 and CrGeTe3, demonstrating intrinsic gap-tunability and topological edge states, advancing potential applications in magnonics and spintronics.

Contribution

It provides the first experimental evidence of topological magnon insulators in 2D vdW ferromagnets with tunable gaps and theoretical demonstration of topological edge states.

Findings

Observation of topological magnon insulators in CrXTe3 (X=Si, Ge).

Confirmation of intrinsic tunability of magnon band gaps.

Theoretical demonstration of in-gap topological edge states.

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.