Giant Response and Harmonic Generation in N\'eel-Torque Antiferromagnetic Resonance

TL;DR

This paper theoretically explores the large nonlinear magnetic responses induced by Neel spin-orbit torques in antiferromagnets, revealing their potential for efficient terahertz frequency conversion and proposing novel nano-device applications.

Contribution

It derives third harmonic susceptibilities showing orders-of-magnitude amplification of magnetic responses due to NSOTs, unveiling their role in nonlinear dynamics and device potential.

Findings

Orders-of-magnitude amplification of magnetic responses by NSOTs

Gigantic harmonic generation enabling terahertz frequency conversion

Proposal of nano-devices for frequency amplification and conversion

Abstract

We theoretically investigate the resonant and higher order magnetic responses of a collinear antiferromagnet induced by N\'eel spin-orbit torques (NSOTs). By deriving the dynamical susceptibilities up to the third harmonic, we find remarkable NSOT-induced amplifications of the linear and nonlinear magnetic dynamics by orders of magnitude compared to conventional spin-orbit torques, enabling highly-efficient frequency conversion in the terahertz frequency range. From the effective dynamics, we uncover the strong coupling between the N\'eel vector and the driving field of NSOTs, providing a physical explanation of the gigantic responses at all orders. We then propose a multilayer antiferromagnetic nano-device leveraging the gigantic harmonic generation to achieve unprecedented frequency amplifiers and converters. Our work uncovers a previously overlooked role of the NSOTs in nonlinear dynamics.