  In previous work we showed that bright atomic solitons can arise in spinor
Bose-Einstein condensates in the form of gap solitons even for repulsive
many-body interactions. Here we further explore the properties of atomic gap
solitons and show that their internal structure can be used to both excite them
and control their center-of-mass motion using applied laser and magnetic
fields. As an illustration we demonstrate a nonlinear atom-optical Mach-Zehnder
interferometer based on gap solitons.
