Band-gap structure and chiral discrete solitons in optical lattices with artificial gauge fields

We study three-leg-ladder optical lattices loaded with repulsive atomic Bose-Einstein condensates and subjected to artificial gauge fields. By employing the plane-wave analysis and variational approach, we analyze the band-gap structure of the energy spectrum and reveal the exotic swallow-tail loop structures in the energy-level anti-crossing regions due to an interplay between the atom-atom interaction and artificial gauge field. In further, we discover stable discrete solitons residing in the forbidden zone above the maxima of the highest band, and we find that these discrete solitons are associated with chiral edge currents.