Vector solitons in parity-time-symmetric lattices.

I study vector solitons involving two incoherently coupled field components in periodic parity-time (PT)-symmetric optical lattices. The specific symmetry of the lattice imposes restrictions on the symmetry of available vector soliton states. While all configurations with asymmetric intensity distributions are prohibited, such lattices support multihump solitons with an equal number of "in-phase" or "out-of-phase" spots in two components, residing on neighboring lattice channels. In the focusing medium, only the solitons containing out-of-phase spots in at least one component can be stable, while in the defocusing medium stability is achieved for structures consisting of in-phase spots. Mixed-gap vector solitons with components emerging from different gaps in the lattice spectrum also exist and can be stable in the PT-symmetric lattice.