Rotons in Gaseous Bose-Einstein Condensates Irradiated by a Laser

A gaseous Bose-Einstein condensate irradiated by a far off-resonance laser has long-range interatomic correlations caused by laser-induced dipole-dipole interactions. These correlations, which are tunable via the laser intensity and frequency, can produce a "roton" minimum in the excitation spectrum--behavior reminiscent of the strongly correlated superfluid liquid He II.