Parametrically driven THz magnon-pairs: Predictions toward ultimately fast and minimally dissipative switching

Finding ways to achieve switching between magnetic states at the fastest possible timescale that simultaneously dissipates the least amount of energy is one of the main challenges in magnetism. Antiferromagnets exhibit intrinsic dynamics in the THz regime, the highest among all magnets, and are, therefore, ideal candidates to address this energy-time dilemma. Here, we study theoretically the THz-driven parametric excitation of antiferromagnetic magnon-pairs at the edge of the Brillouin zone and explore the potential for switching between two stable oscillation states. Using a semi-classical theory, we predict that switching can occur at the femtosecond timescale with an energy dissipation down to a few zepto Joule. This result touches the thermodynamical bound of the Landauer principle and approaches the quantum speed limit up to 5 orders of magnitude closer than demonstrated with magnetic systems so far.