External Josephson Effect in BEC

Andrea Spuntarelli, P. Pieri, Giancarlo Calvanese Strinati

Fernando Sols

I present an overview of the physics of the Josephson effect between Bose condensed systems, with emphasis on the recently achieved BEC's in trapped alkali gases. I focus mostly on those physical phenomena that are likely to be observed only (or more easily) in these novel systems. Thus I omit the discussion of problems which may be viewed as straightforward applications of well known Josephson physics. In particular, I review the external and the internal Josephson effects, and discuss how in the latter case it may be possible to explore the crossover between collective Josephson behavior and independent boson Rabi dynamics. I also describe novel macroscopic quantum phenomena such as self-trapping and interference between separate Bose condensates.

M. Grether, MANUEL DE LLANO

Dan-Wei Zhang, Libin Fu, Z. D. Wang +1 more

We investigate the quantum dynamics of an experimentally realized spin-orbit-coupled Bose-Einstein condensate in a double-well potential. The spin-orbit coupling can significantly enhance the atomic interwell tunneling. We find the coexistence of internal and external Josephson effects in the system, which are moreover inherently coupled in a complicated form even in the absence of interatomic interactions. Moreover, we show that the spin-dependent tunneling between two wells can induce a net atomic spin current referred as spin Josephson effects. Such spin Josephson effects can be observable under realistic conditions.

Łukasz A. Turski

Elena A. Ostrovskaya, Yuri S. Kivshar, M. Lisak +3 more

We apply the concepts of nonlinear guided-wave optics to a Bose-Einstein condensate (BEC) trapped in an external potential. As an example, we consider a parabolic double-well potential and derive coupled-mode equations for the complex amplitudes of the BEC macroscopic collective modes. Our equations describe different regimes of the condensate dynamics, including the nonlinear Josephson effect for any separation between the wells. We demonstrate macroscopic self-trapping for both repulsive and attractive interactions, and confirm our results by direct numerical solution of the Gross-Pitaevskii-equation.