Internal Josephson phenomena in a coupled two-component Bose condensate

• Internal oscillations between the two states of a condensate are investigated.
• Main controlling parameter of the system is the energy detuning between the states.
• The system can exhibit modified harmonic and anharmonic Rabi oscillations.
• Possible transition to an internal a.c. Josephson regime is demonstrated.
• At a certain value of the detuning the internal oscillations are fully suppressed.

We discuss coherent oscillations between two coupled quantum states of a Bose–Einstein condensate in two-dimensional space at zero temperature. In the system we consider, weak interparticle repulsive interactions occur between the particles in state one only, while the state two particles remain non-interacting. Our theoretical analysis of the coupled generalized Gross–Pitaevskii equations reveals various regimes of oscillatory dynamics for the relative phase and population imbalance between the two subsystems of the condensate, with the energy detuning between the two states being the controlling parameter of the system.