Observation of a localized flat-band state in a photonic Lieb lattice
  We show experimentally how a non-diffracting state can be excited in a photonic Lieb lattice. This lattice supports three energy bands, including a perfectly flat middle band, which corresponds to an infinite effective mass with zero dispersion. We show that a suitable optical input state can be prepared so as to only excite the flat band. We analyse, both experimentally and theoretically, the evolution of such photonic flat-band states, and show their remarkable robustness, even in the presence of disorder. 
Sebabrata Mukherjee, Alexander Spracklen, Debaditya Choudhury, Nathan   Goldman, Patrik \"Ohberg, Erika Andersson and Robert...
physics.optics cond-mat.quant-gas