Hofstadter's Butterfly

When graphene is placed in contact with hexagonal boron, a moire pattern develops with long range order, which in turn looks like a crystal field to the free electrons in the graphene layer.  We were able to exploit the large length-scale of the moire superlattice  (~15 nm) to observe the long predicted Hofstadter butterfly fractal energy spectrum - a result physicists have been chasing for more than 30 years!  Our resuls appeared in the magazine Nature .

-UPDATE- Physics world has identified our results as one of the "top ten breakthroughs of 2013".