Oscillating Quantum Droplets From the Free Expansion of Logarithmic One-dimensional Bose Gases

We analyse some issues related to the stability and free expansion of a one-dimensional logarithmic Bose–Einstein condensate, particularly its eventual relation to the formation of quantum droplet-type configurations. We prove that the corresponding properties, such as the energy of the associated N-body ground state, differ substantially with respect to its three-dimensional counterpart. Consequently, the free velocity expansion also shows remarkable differences with respect to the three-dimensional system when logarithmic interactions are taken into account. The one-dimensional logarithmic condensate tends to form quantum droplet-type configurations when the external trapping potential is turned off, i.e., the self-sustainability or self-confinement appears as in three-dimensions. However, we obtain that for some specific values of the self-interaction parameters and the number of particles under consideration, the cloud oscillates during the free expansion around to a specific equilibrium size. These results show that we are able to describe scenarios in which the one-dimensional cloud reaches stable configurations, i.e., oscillating quantum droplets.