Voltage-Controlled High-Bandwidth Terahertz Oscillators Based On Antiferromagnets

The terahertz (THz) technology gap refers to a frequency range of electromagnetic radiation in the THz regime where current technologies are inefficient for generating and detecting radiation. Here, we show that noncollinear antiferromagnets (NCAFM) with kagome structure host gapless self-oscillations whose frequencies are tunable from 0 Hz to the THz regime via electrically induced spin-orbit torques (SOTs) [1]. The auto-oscillations' initiation, bandwidth, and amplitude are investigated by deriving an effective theory, which captures the reactive and dissipative SOTs. We find that the dynamics strongly depends on the ground state's chirality, with one chirality having gapped excitations, whereas the opposite chirality provides gapless self-oscillations. Our results demonstrate that NCAFMs offer unique THz functional components, which could play a significant role in bridging the gap between technologies operating in the microwave and infrared regions. [1] M. A. Lund, D. R. Rodrigues, K. Everschor-Sitte, and K. M. D. Hals, Phys. Rev. Lett. 131, 156704 (2023).