Soliton sheets of Bose-Einstein condensates in optical lattices

Soliton sheets are observed in Bose-Einstein condensates in optical lattice which are formed by superposition of condensates occupying different single-particle states. These structures consist of one-dimensional stationary solitons distributed in the x-direction arranged continuously along the peaks of the optical lattice in the y-direction. Notably, the phase difference across the soliton sheets is periodic and varies linearly with y within each period. So, we refer to this configuration as a 'soliton sheet'. A velocity difference in the y-component is observed between the two sides of the soliton sheets. Similar velocity distributions can be achieved by aligning an infinite number of isotropic vortices along the peaks of the optical lattice. And the soliton sheets are distinguished by their lack of dependence on phase singularities. This independence enables the formation of soliton sheets even in the absence of phase singularities, highlighting a unique aspect of this structure.