title: Twin-vortex solitons in nonlocal nonlinear media.
abstract: We consider soliton formation in thermal nonlinear media bounded by rectangular cross sections and uncover what we believe to be a new class of nonlinear stationary topological state. Specifically, we find that stationary higher-order vortex states in standard shapes do not exist, but rather they take the form of multiple spatially separated single-charge singularities nested in an elliptical beam. Double-charge states are found to be remarkably robust despite their shape asymmetry and phase-singularity splitting. States with higher topological charges are found to be unstable.
authors.affiliation: Department of Physics, Centre for Nonlinear Studies, and The Beijing-Hong Kong-Singapore Joint Centre for Nonlinear and Complex Systems, Hong Kong Baptist University, Kowloon Tong, China. fwye@hkbu.edu.hk
authors.forename: Fangwei
authors.initials: F
authors.lastname: Ye
authors.forename: Yaroslav V
authors.initials: YV
authors.lastname: Kartashov
authors.forename: Bambi
authors.initials: B
authors.lastname: Hu
authors.forename: Lluis
authors.initials: L
authors.lastname: Torner