Terahertz high-harmonic generation in gapped antiferromagnetic chains

TL;DR

This paper explores how linear and quadratic spin-phonon couplings in gapped antiferromagnetic chains influence high-harmonic generation in the THz regime, providing insights for nonlinear magnonics and spintronic applications.

Contribution

It introduces a theoretical analysis of high-harmonic generation mechanisms in antiferromagnetic chains considering spin-phonon couplings using spin-wave, mean-field, and Lindblad formalisms.

Findings

Quadratic SPC blocks odd harmonics due to inversion symmetry.

Linear SPC generates both odd and even harmonics.

Drive frequency and damping affect harmonic spectrum.

Abstract

The nonlinear dynamics of magnetization in antiferromagnets, resulting in high-frequency spin waves (high-order harmonics) as signal carriers, enable fast magnetic state switching in spintronic devices. More harmonic orders potentially allow more information to be conveyed by the spins. Developing theoretical models to describe these waves in antiferromagnets is essential for predicting their properties and guiding experimental efforts. Here, we consider the role of linear and quadratic spin-phonon couplings (SPCs) in achieving high-order harmonics in the THz magnetization of a gapped antiferromagnetic spin chain. A THz steady laser's electric field indirectly drives spins via phonons. Using spin-wave theory, mean-field theory, and the Lindblad formalism, we analyze the resulting nonlinear dynamics. We highlight the distinct mechanisms for harmonic generation when a phonon is coupled to the easy-plane and easy-axis of spins. Moreover, we observe that quadratic SPC blocks odd harmonics due to invariant inversion symmetry, while linear SPC generates both odd and even harmonics. We also investigate the effects of drive frequency, drive amplitude, phonon damping, and spin damping on the number of harmonics. Our findings offer an alternative pathway for developing nonlinear magnonics.