Dark-type solitons in media with competing nonlocal non-Kerr nonlinearities

We address the properties of dark-type solitons, including dark solitons and darklike bright solitons, based on a phenomenological model for a nonlocal medium featuring competing cubic-quintic nonlinearities [Phys. Rev. E 74 66614 (2006)]. We consider two forms of such nonlinearities: focusing cubic and defocusing quintic nonlinearities, and defocusing cubic and focusing quintic nonlinearities. We reveal that nonlocality drastically modifies shapes, velocity, existence properties, and stability properties of dark-type solitons. At suitable parameter regions, nonlocality could impose strong restrictions on soliton existence or exhibit remarkable destabilizing action on darktype solitons. The stability of single dark-type solitons exactly obeys the stability criterion for dark solitons. Collisions between dark-type solitons and their bound states are also investigated.