Direct observation of topological magnon edge states

TL;DR

This study provides direct, spatially-resolved evidence of topological magnon edge states in a single-layer ferromagnetic material, advancing understanding of magnonic topological insulators and their potential applications.

Contribution

We experimentally observed and spatially resolved magnon edge states in a 2D ferromagnet, confirming the existence of magnon Chern insulator states at the single-layer level.

Findings

Detected magnon edge states at three different edge configurations.

Observed magnon spectra with enhanced signals at van Hove singularities.

Provided direct evidence of topological magnon states in a 2D ferromagnet.

Abstract

Magnon Chern insulators (MCIs) exhibit unique topological magnon band structures featuring chiral edge states. Direct observations of the topologically protected magnon edge states have long been pursued. Here, we report the spatially resolved detection of magnon edge states in a two-dimensional ferromagnet with honeycomb lattice (single-layer chromium triiodide). Using scanning tunneling microscopy, we observed magnon-assisted inelastic tunneling conductance and revealed the gapped magnon spectra with enhanced signals at the van Hove singularities. Extra tunneling conductance contributed from the magnon edge states was detected at three different edge configurations. Our work provided direct evidence proving the existence of MCI states down to the single-layer limit, initiating spatially-resolved explorations on exotic properties arising from topological edge states of MCIs.