Graphene consists of a single layer of carbon atoms arranged in a pattern similar to that of chicken wire. Like two pieces of a nylon curtain or two haphazardly stacked screens, a moire pattern is formed when two periodic configurations are overlaid with a relative twist. In periodic systems of atoms, the electronic spectrum consists of continuous bands of "allowed" electron energies separated by gaps that denote "forbidden" values. Rafi Bistritzer and Allan MacDonald (pp. 12233-12237) suggest that for two overlaid graphene layers twisted at arbitrary small angles, the atoms' moire pattern leads to moire energy bands, which reflect the periodicity of the moire pattern rather than that of the underlying chicken wire pattern.
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