Did you know that if you put two sheets of graphene together and rotate them to a so-called "magic" angle, the innermost bands become flat - meaning the momentum doesn't depend on energy so the particles can change momentum without needing to gain or lose energy. [1/2]
This means many-particle effects are important, perhaps creating conditions for superconductivity, just by twisting two layers of graphene! Above are miniband structures I calculated for the angle being 2° - you can see Dirac cones with some dispersion - and 1.1°, a magic angle for which flat bands appear. [2/2]
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