Figure 1
J. Krauser/Univ. of Hamburg

Band mapping. Researchers have mapped the energy states or “bands” of cold fermionic atoms in a lattice of laser light, using them as a model for electrons in real crystals. This momentum distribution shows the atoms when they’re all in the lowest energy band (foreground) and after some have been excited into the third band (the “wings” in the middle and background). The “dents” in the central peak are the “holes” left behind by excited atoms.