https://www.sciencedaily.com/releases/2018/05/180523133205.htm > Columbia investigators have made a major breakthrough in this research, with their invention of a novel "home-built" cryogenic near-field optical microscope that has enabled them to directly image, for the first time, the propagation and dynamics of graphene plasmons at variable temperatures down to negative 250 degrees Celsius. The study was published online today in Nature. > "Our temperature-dependent study now gives us direct physical insight into the fundamental physics of plasmon propagation in graphene," says Dimitri N. Basov, professor of physics at Columbia University, who led the study together with colleagues Cory Dean (physics) and James Hone (mechanical engineering, Columbia Engineering). "This insight was impossible to attain in previous nanoimaging studies done at room temperature. We were particularly surprised at discovering, after many years of failed attempts to get anywhere close, that compact nanolight can travel along the surface of graphene for distances of many tens of microns without unwanted scattering. The physics limiting the travel range of nanolight is a fundamental finding of our study and may lead to new applications in sensors, imaging, and signal processing."