They then added a layer of graphene in order to apply an electric voltage with which the density of electrons in the material could be controlled. (sciencedaily.com)
By adjusting various parameters — such as the density of conduction electrons in the material or the strength of the DC electric field — it is possible to tune the cutoff wavenumber and, consequently, the frequency of the resulting terahertz radiation. (sciencedaily.com)
Until recently, there were no experimental reports of superconductivity in graphene although its close relatives, graphite and fullerenes can be made superconducting by intentionally introducing electrons in the material (doping). (sciencedaily.com)