Boosting Superconductivity in Graphene Bilayers

Nearly a decade ago, researchers heralded the discovery of a new wonder class of ultrathin materials with special optical and electrical properties that made it a potential rival for graphene, a form of carbon discovered in 2004 whose own special properties interest both scientists and engineers. Now, Caltech engineers have shown that one of these wonder materials, tungsten diselenide, is not just a rival to graphene but also a complement to it. By adding tungsten diselenide to graphene, they have managed to enhance the graphene's electrical properties in ways that enrich our understanding of superconductivity and pave the way for engineering more robust and highly tunable graphene-based superconductors. To understand what the researchers have accomplished, it is helpful to first know what graphene is and why its properties make it useful. Graphene is a form of carbon consisting of a single layer of atoms arranged in a honeycomb-like lattice pattern that looks like chicken wire. When two or more of these sheets are stacked on top of each other, the resulting material can exhibit vastly different electronic properties depending on the alignment of those sheets in relation to one another. For instance, when the second sheet of graphene is "twisted" by just 1.05 degrees (a value known as the "magic angle") in relation to the sheet it is laid on top of, the resulting stack can be either a superconductor that conducts electricity with absolutely no resistance whatsoever or an insulator that completely blocks the passage of electricity.