Beyond the mean-field approximation

Ingo Homrighausen, Stefan K. Kehrein

G C Katsimiga, G M Koutentakis, S I Mistakidis +2 more

The dynamics of dark–bright (DB) solitons beyond the mean-field approximation is investigated. We first examine the case of a single DB soliton and its oscillations within a parabolic trap. Subsequently, we move to the setting of collisions, comparing the mean-field approximation to that involving multiple orbitals in both the dark and the bright component. Fragmentation is present and significantly affects the dynamics, especially in the case of slower solitons and in that of lower atom numbers. It is shown that the presence of fragmentation allows for bipartite entanglement between the distinguishable species. Most importantly the interplay between fragmentation and entanglement leads to the splitting of each of the parent mean-field DB solitons, placed off-center within the parabolic trap, into a fast and a slow daughter solitary wave. The latter process is in direct contrast to the predictions of the mean-field approximation. A variety of excitations including DB solitons in multiple (concurrently populated) orbitals is observed. Dark–antidark states and domain-wall-bright soliton complexes can also be observed to arise spontaneously in the beyond mean-field dynamics.

Tomoyasu Tanaka

P. I. Khadzhi

The occurrence of optical echo phenomena in two-level media is analyzed beyond the mean field approximation. The polarization of the medium and the intensity of the echo signal depend in a complex way on both the areas of the pulses and on the area of the `material' field and the relation between (on the one hand) the photon densities of each pulse and (on the other) the density of two-level atoms (excitons) of the medium.

Andreas Wipf