SCIENCE - Two teams use cold atoms and lasers to create a system that should exhibit Hofstadter's butterfly

(Phys.org) —Two teams working independently of each other have created systems that are expected to exhibit Hofstadter excitations (a butterfly). One team was run by lead researchers at the University of Munich and the Max Planck Institute in Germany, the other by a team at MIT. Both have published papers in the journal Physical Review Letters, detailing their nearly identical systems and results ...

http://phys.org/news/2013-10-teams-cold-atoms-lasers-hofstadter.htm