Phase Transition in Interacting Boson System at Finite Temperatures

Thermodynamical properties of an interacting boson system at finite temperatures and zero chemical potential are studied within the framework of the Skyrme-like mean-field toy model. It is assumed that the mean field contains both attractive and repulsive terms. Self-consistency relations between the mean field and thermodynamic functions are derived. It is shown that for sufficiently strong attractive interactions this system develops a first-order phase transition via formation of Bose condensate. An interesting prediction of the model is that the condensed phase is characterized by a constant total density of particles. The thermodynamical characteristics of the system are calculated for the liquid-gas and condensed phases. The energy density exhibits a jump at the critical temperature.