I haven't studied both the original link and your link in detail, but at a quick look: They are different things. Metamaterials usually are periodic combinati

I haven't studied both the original link and your link in detail, but at a quick look: They are different things. Metamaterials usually are periodic combinations that exhibit interesting properties. So-called "photonic bandgap materials" are an example. The paper you linked shows that strange things can happen to the group velocities in these types of materials. The phys.org link (based on a Science paper [1]) is about a cavity utilizing non-reciprocal materials. Normally systems involving Maxwell's equations are reciprocal; you can switch the input and output and expect the same behavior. For a basic example, if you look through a tube and see me at the other end, then I will be able to see you as well. In a non-reciprocal system, this property breaks down. Microwave circulators are a good example: A device with three ports A, B, and C can have energy coming from A going to B, energy coming from B going to C, energy coming from C going to A. This device is handy if you don't want reflected E&M power from your antenna coming back into your generating circuit. It was well known to guys working on radar, for example. The real miracle in this paper is that no one put it together sooner: Non-reciprocal devices have been around forever, and resonators more so, but that the combination might be useful has not occurred to anyone? Quite amazing. They probably blew all kinds of time researching through old literature to make sure this hasn't already been mentioned by the radar guys in the 40s. [1] http://science.sciencemag.org/content/356/6344/1260 http://science.sciencemag.org/content/356/6344/1260