Terahertz Nonlinear Magnonics

Jan 26, 2023 (Friday) at 12PM (ET)

Zhuquan Zhu

MIT

Coherent excitations of magnetically ordered materials, referred to as spin waves and their quanta, magnons, have emerged as prominent candidates for interference-based signal processing technologies. Despite the growing interest in manipulating magnonic states beyond thermodynamic equilibrium, elucidating and inducing coherent couplings between distinct magnon modes remains a long-standing challenge. In this talk, I will highlight our recent work, where we demonstrate coherent nonlinear magnon-magnon interactions in antiferromagnets driven by tailored terahertz fields. Leveraging two-dimensional terahertz polarimetry techniques with single-shot detection [1], we observed a unidirectional magnon upconversion process [2] and identified correlated magnonic signals at both the sum and difference frequencies of the two magnon modes [3]. By tuning the difference frequency generation signal to match the energy of the low-frequency magnon mode, we achieved parametric amplification of the magnon signal [4]. These findings offer valuable insights into nonlinear magnonics in antiferromagnets, extending the frontiers of spintronics and magnonics into the ultrafast nonlinear regime.

[1] Gao, F. Y., Zhang, Z., Liu, Z.-J. & Nelson, K. A. High-speed two-dimensional terahertz spectroscopy with echelon-based shot-to-shot balanced detection. Opt. Lett. 47, 3479–3482 (2022).

[2] Zhang, Z. et al. Terahertz field-driven magnon upconversion in an antiferromagnet. Nature Physics (2024).

[3] Zhang, Z. et al. Terahertz field-induced nonlinear coupling of two magnon modes in an antiferromagnet. Nature Physics (2024).

[4] Zhang, Z. et al. Terahertz stimulated parametric downconversion of a coherent magnon mode in an antiferromagnet. Submitted.