L. Reatto et al., BOSONIC CLOUDS WITH ATTRACTIVE INTERACTION BEYOND THE LOCAL INTERACTION APPROXIMATION, Journal of low temperature physics, 113(3-4), 1998, pp. 195-200
We study the properties of a Bose-Einstein condensed cloud of atoms wi
th negative scattering length confined in a harmonic trap. When a real
istic non local (finite range) effective interaction is taken into acc
ount, we find that, besides the known low density metastable solution,
a new branch of Bose condensate appears at higher density. This state
is self-bound but its density can be quite low if the number N of ato
ms is not too big. The transition between the two classes of solutions
as a function of N can be either sharp or smooth according to the rat
io between the range of the attractive interaction and the length of t
he trap. A tight trap bads to a smooth transition. In addition to the
energy and the shape of the cloud we study also the dynamics of the sy
stem. In particular, we study the frequencies of collective oscillatio
n of the Bose condensate as a function of the number of atoms both in
the local and in the non local case. Moreover, we consider the dynamic
s of the cloud when the external trap is switched off.