Preprint at http://arxiv.org/abs/1308.2931 (2013)

In digital electronics applications, the use of graphene-based transistors is hampered by the difficulty of defining clearly separated on and off states for the current. This difficulty is due to the absence of an intrinsic energy bandgap, which at present cannot be introduced artificially without affecting the excellent transport properties of graphene. Now, Guanxiong Liu and collaborators overcome this limitation by taking advantage of the nonlinear output characteristics of graphene-based transistors. Using a diode-like biasing configuration they demonstrate that the current flowing in the device decreases when the applied voltage increases, unlike the behaviour observed in linear resistors. This negative resistance is the key to realizing high-speed electronic circuits, which can be used as building blocks both for Boolean and non-Boolean logic operations. Importantly, this nonlinearity is also theoretically demonstrated for nanosized transistors operating in the ballistic transport regime, paving the way for the realization of high-density electronic circuits based on graphene.