Depletion of a Bose–Einstein condensate by laser-induced dipole–dipole interactions

We study a gaseous atomic Bose–Einstein condensate with laser-induced dipole–dipole interactions using the Hartree–Fock–Bogoliubov theory within the Popov approximation. The dipolar interactions introduce long-range atom–atom correlations which manifest themselves as increased depletion at momenta similar to that of the laser wavelength, as well as a 'roton' dip in the excitation spectrum. Surprisingly, the roton dip and the corresponding peak in the depletion are enhanced by raising the temperature above absolute zero.