Magnon-Phonon coupling in Fe$_3$GeTe$_2$

TL;DR

This study demonstrates strong magnon-phonon coupling in Fe3GeTe2 using inelastic scanning tunneling spectroscopy, revealing hybridized magnonic and phononic bands and providing insights for designing dynamic coupling in 2D materials.

Contribution

First experimental demonstration of strong magnon-phonon coupling in Fe3GeTe2 using ISTS, with detailed analysis of hybridization and comparison to theoretical calculations.

Findings

Identification of hybrid magnon-phonon bands

Observation of van Hove singularities due to avoided crossings

Agreement between experimental data and density functional theory

Abstract

We study the dynamic coupling of magnons and phonons in single crystals of Fe3GeTe2 (FGT) using inelastic scanning tunneling spectroscopy (ISTS) with an ultra-low temperature scanning tunneling microscope. Inelastic scattering of hot carriers off phonons or magnons has been widely studied using ISTS, and we use it to demonstrate strong magnon-phonon coupling in FGT. We show a strong interaction between magnons and acoustic phonons which leads to formation of van Hove singularities originating in avoided level crossings and hybridization between the magnonic and phononic bands in this material. We identify these additional hybridization points in experiments and compare their energy with density functional theory calculations. Our findings provide a platform for designing the properties of dynamic magnon-phonon coupling in two-dimensional materials.