Gap solitons supported by optical lattices in photorefractive crystals   with asymmetric nonlocality
  We address the impact of asymmetric nonlocal diffusion nonlinearity on the properties of gap solitons supported by photorefractive crystal with an imprinted optical lattice. We reveal how the asymmetric nonlocal response alters the domains of existence and the stability of solitons originating from different gaps. We find that in such media gap solitons cease to exist above a threshold of the nonlocality degree. We discuss how the interplay between nonlocality and lattice strength modifies the gap soliton mobility. 
Zhiyong Xu, Yaroslav V. Kartashov, and Lluis Torner