Collision interference effects in a bose-einstein gas

Xiaowei Yang, Ying Wu

Fabio Lingua, Luca Lepori, F. Minardi +2 more

Thomas G. Wong, Matthew J. Collett, Daniel F. Walls

We extend the work of Javanainen and Yoo [Phys. Rev. Lett. 76, 161 (1996)] on the interference between two Bose-Einstein condensates to include the effects of collisions. The competing effects of the atomic detections that establish phase coherence and the decohering effects of the collisions are computed using the Monte Carlo wave-function method. Limits to the tolerance of the condensate phase to atomic collisions are established.

Mehmet Özgür Oktel, Leonid S Levitov

Optical excitations in a Bose gas are demonstrated to be sensitive to many-body effects. At low temperature the momentum relaxation is provided by momentum exchange collisions, rather than by elastic collisions. A collective excitation mode forms, which in a nondegenerate gas is manifest in a collision shift and dramatic narrowing of spectral lines. In the Bose-Einstein condensate state, each spectral line splits into two components. The doubling of the optical excitations results from the physics analogous to that of the second sound. We present a theory of the line doubling, and calculate optical absorption spectrum for a uniform density system.

Mehmet Özgür Oktel, Leonid S Levitov

A theory for the Rabi and internal Josephson effects in an interacting, homogeneous Bose-Einstein gas in the cold collision regime is presented. By using the microscopic transport equation for the density matrix the problem is mapped onto a problem of precession of two coupled classical spins. In the absence of an external excitation field our results agree with the theory of density induced frequency shifts in atomic clocks. In the presence of the external field, the internal Josephson effect occurs in a condensed Bose-Einstein gas as well as in a noncondensed gas. The crossover from Rabi oscillations to Josephson oscillations as a function of interaction strength is studied in detail.

Xuguang Yue, Shujuan Liu, Hongwei Xiong