Correlations in a two-dimensional Bose gas with long-range interaction

We study the correlations of two-dimensional dipolar bosons with excitons in semiconductor bilayers as a specific case, in the whole temperature- concentration region. We show that at low concentrations, the Bose degeneracy is accompanied by strong multi-particle correlations and the system behaves as a Bose liquid. At high concentrations the repulsion suppresses quantum coherence and the system behaves as a classical liquid down to a temperature lower than typical for a Bose gas. The interaction energy of the particles is a sensitive tool for a measurement of the correlations. This theory can apply to other systems of bosons with extended interaction.