Light-induced weak ferromagnetism through nonlinear magnonic rectification

TL;DR

This paper introduces nonlinear magnonic rectification, a process where light excites chiral phonons in antiferromagnets, leading to a quasistatic magnetization and demonstrating a new form of light-induced weak ferromagnetism.

Contribution

The paper proposes and theoretically demonstrates a novel mechanism for inducing weak ferromagnetism via nonlinear magnonic rectification in antiferromagnets with chiral phonon modes.

Findings

Quasistatic magnetization can be generated by transient spin canting.

Chiral phonon excitation produces an effective magnetic field for spins.

This mechanism enables light-induced weak ferromagnetism in magnetic systems.

Abstract

Rectification describes the generation of a quasistatic component from an oscillating field, such as an electric polarization in optical rectification, or a structural distortion in nonlinear phononic rectification. Here, we present a third fundamental process for magnetization, in which spin precession is rectified along the coordinates of a nonlinearly driven magnon mode in an antiferromagnet. We demonstrate theoretically that a quasistatic magnetization can be induced by transient spin canting in response to the coherent excitation of a chiral phonon mode that produces an effective magnetic field for the spins. This mechanism, which we call nonlinear magnonic rectification, is generally applicable to magnetic systems that exhibit infrared-active chiral phonon modes. Our results serve as an example of light-induced weak ferromagnetism and open a promising avenue towards creating dynamical spin configurations that are not accessible in equilibrium.