Josephson tunneling between weakly interacting Bose-Einstein condensates -art. no. 033610

Based on a tunneling Hamiltonian description. we calculate the Josephson, n ormal, and interference currents between two Bose-Einstein condensates desc ribed by the Bogoliubov theory. The dominant Josephson term is of first ord er in the tunneling with a critical current density proportional to the gro und state pressure. In contrast to superconductors, the normal current rema ins finite at zero temperature. We discuss the dynamics of the relative pha se in a semiclassical approximation derived from an exact functional integr al approach, which includes the interaction effects at fixed total particle number. It is shown that the normal current leads to a damping of the Jose phson oscillations and, at long times, eliminates the macroscopic quantum s elf-trapping predicted by Smerzi et al. Finally, we give estimates for an e xperimental realization of Josephson tunneling in cold atomic gases, which indicate that coherent transfer of atoms might be realized with a Na-23 con densate.