Coherently driven 2-component Bose gases (Dr. A. Recati)

The Rabi term reduces the gauge symmetry of the system and a gap opens for relative phase excitations. The latter has many consequences. In particular it leads to the formation of vortex dimers coupled through sine-Gordon solitons. Results on the dynamics of the vortex dimer are presented. The system exhibits also a second order (quantum) phase transition between a neutral (paramagnetic) and a polarised (ferromagnetic) state, provided the interspecies interaction is large enough. I will discuss some phenomena related to the phase transition and to the two phases and the interplay between Rabi coupling and density-density interaction: (i) at a mean-field level for a continuous model - which well described atoms in a shallow trap. (ii) for a one-dimensional single band Hubbard model - which describes atoms confined in an one-dimensional optical lattice.