Negative refraction achieved propagating light through atomic arrays, without need for artificially manufactured metamaterials

https://www.eurekalert.org/news-releases/1073130

"negative refraction: light in medium bends in opposite direction to what is typically observed in nature,potentially enabling perfect lens capable of focusing/ imaging beyond diffraction limit, or cloaking devices rendering objects invisible... overcomes metamaterial fabrication imperfections/ non-radiative losses... atoms interact collectively enabling negative refraction... trapping atoms in periodic optical lattices providing pristine, clean medium free from fabrication imperfections, without absorption losses"