in bilayer systems have been shown theoretically to carry a supercurrent. Superconductivity in twisted bilayer graphene Pablo Jarillo-Herrero of MIT and colleagues from Harvard and the National Institute for Materials Science, Tsukuba, Japan, have reported the discovery of superconductivity in bilayer graphene with a twist angle of 1.1° between the two layers. The discovery was announced in Nature in March 2018. The findings confirmed predictions made in 2011 by Allan MacDonald and Rafi Bistritzer that the amount of energy a free electron would require to tunnel between two graphene sheets radically changes at this angle. The graphene bilayer was prepared from exfoliated monolayers of graphene, with the second layer being manually rotated to a set angle with respect to the first layer. A critical temperature of was observed with such specimens in the original paper (with newer papers reporting slightly higher temperatures). Jarillo-Herrero has suggested that it may be possible to “...... imagine making a superconducting transistor out of graphene, which you can switch on and off, from superconducting to insulating. That opens many possibilities for quantum devices.” The study of such lattices has been dubbed "twistronics" and was inspired by earlier theoretical treatments of layered assemblies of graphene. Field effect transistors Bilayer graphene can be used to construct field effect transistors or tunneling field effect transistors, exploiting the small energy gap. However, the energy gap is smaller than 250 meV and therefore requires the use of low operating voltage (< 250 mV), which is too small to obtain reasonable performance for a field effect transistor, but is very suited to the operation of tunnel field effect transistors, which according to theory from a paper in 2009 can operate with an operating voltage of only 100 mV. In 2016 researchers proposed the use of bilayer graphene to increase the output voltage of tunnel transistors (TT). They operate at a lower operating voltage range (150 mV) than silicon transistors (500 mV). Bilayer graphene's energy band is unlike that of most semiconductors in that the electrons around the edges form a (high density) van Hove singularity. This supplies sufficient electrons to increase current flow across the energy barrier. Bilayer graphene transistors use "electrical" rather than "chemical" doping. Ultrafast lithium diffusion In 2017 an international group of researchers showed that bilayer graphene could act as a single-phase mixed conductor which exhibited Li diffusion faster than in graphite by an order of magnitude. In