# Orbital magnetic moments of phonons

## TL;DR

This paper calculates the orbital magnetic moments of phonons in various materials, exploring their potential for inducing magnetic effects via laser excitation and magnetic fields, and providing a comprehensive guide for future research in phonon-driven phenomena.

## Contribution

It introduces a systematic computational approach to evaluate phonon orbital magnetic moments across multiple materials, highlighting factors influencing their magnitude and potential applications.

## Key findings

- Large phonon orbital magnetic moments identified in certain materials.
- Quantitative estimates of phonon-induced magnetic effects under laser excitation.
- Insights into chiral phonons and their intrinsic circular motions.

## Abstract

In ionic materials, circularly polarized phonons carry orbital magnetic moments that arise from circular motions of the ions, and which interact with other magnetic moments or fields. Here, we calculate the orbital magnetic moments of phonons in 35 different materials using density functional theory, and we identify the factors that lead to, and materials that show, large responses. We compute the resulting macroscopic orbital magnetic moments that can be induced by the excitation of coherent phonons using mid-infrared laser pulses, and we evaluate the magnitudes of the phonon Zeeman effect in a strong magnetic field. Finally, we apply our formalism to chiral phonons, in which the motions of the ions are intrinsically circular. The zoology presented here may serve as a guide to finding materials for phonon and spin-phonon driven phenomena.