Terahertz Antiferromagnetic Spin Hall Nano-Oscillator

TL;DR

This paper explores the dynamics of antiferromagnetic insulators driven by spin Hall effects, demonstrating the potential for terahertz oscillators with controllable amplitude and chirality.

Contribution

It introduces a model for current-induced oscillations in antiferromagnets, revealing conditions for steady-state terahertz oscillations and the role of feedback mechanisms.

Findings

Oscillations occur between acoustic and optical modes at high currents.

Current direction controls the chirality of oscillations.

Steady-state oscillations are achievable with feedback effects.

Abstract

We consider the current-induced dynamics of insulating antiferromagnets in a spin Hall geometry. Sufficiently large in-plane currents perpendicular to the N\'{e}el order trigger spontaneous oscillations at frequencies between the acoustic and the optical eigenmodes. The direction of the driving current determines the chirality of the excitation. When the current exceeds a threshold, the combined effect of spin pumping and current-induced torques introduces a dynamic feedback that sustains steady-state oscillations with amplitudes controllable via the applied current. The ac voltage output is calculated numerically as a function of the dc current input for different feedback strengths. Our findings open a route towards terahertz antiferromagnetic spin-torque oscillators.