An international research team lead by Aalto University has found a new and simple route to break the reciprocity law in the electromagnetic world, by changing a material's property periodically in time. The breakthrough could help to create efficient nonreciprocal devices, such as compact isolators and circulators, that are needed for the next generation of microwave and optical communications systems.
source https://phys.org/news/2020-12-reciprocity-law.html
