Non-Hermitian Topological Magnonics

Frequency combs involve generating a series of signals with equal frequency differences. For example, if input f1 and f2 are given, the output signal will have a frequency difference of f1 minus f2. The figure demonstrates that the number of tones in the comb is enhanced at the exceptional point due to increased sensitivity to perturbations.

Next, I will explain how exceptional points can be achieved in magnetic heterostructures. For instance, exceptional points have been suggested in measurements of ferromagnet-normal metal and ferromagnet-heterostructures.