Symmetry-forbidden intraband transitions leading to ultralow Gilbert damping in van der Waals ferromagnets

TL;DR

This study reveals that mirror symmetry in 2D van der Waals ferromagnets suppresses intraband transitions, leading to ultralow Gilbert damping, with potential for designing energy-efficient spintronic devices.

Contribution

It demonstrates the role of mirror symmetry in suppressing damping and explores how symmetry breaking increases damping, providing new insights into 2D ferromagnet spin dynamics.

Findings

Ultralow Gilbert damping occurs at weak scattering due to mirror symmetry.

Breaking mirror symmetry increases damping by enabling intraband transitions.

Topological nodal lines significantly contribute to damping and can be tuned by Fermi level.

Abstract

Based upon first-principles calculations, we report ultralow Gilbert damping in two-dimensional (2D) van derWaals (vdW) ferromagnets. The low damping occurs at weak scattering because mirror symmetry prohibits intraband transitions. The monotonic dependence on the electronic scattering rate suggests the absent lower limit, in contrast to conventional ferromagnetic materials. Breaking mirror symmetry through magnetization rotation, layer stacking, or structural phase transition significantly increases damping by enabling intraband transitions. Topological nodal lines, also protected by mirror symmetry, contribute substantially to interband-transition-mediated damping, which can be tuned by adjusting the Fermi level. Our findings elucidate the unique characteristics of Gilbert damping in 2D vdW ferromagnets, providing valuable insights for designing low-dimensional spintronic devices with high energy efficiency.