Long range dipole-dipole interaction in low-density atomic vapors probed by double-quantum two-dimensional coherent spectroscopy

Optical double-quantum two-dimensional coherent spectroscopy (2DCS) was implemented to probe interatomic dipole-dipole interactions in both potassium and rubidium atomic vapors. The dipole-dipole interaction was detected at densities of 4.81 x 10(8) cm(-3) and 8.40 x 10(9) cm(-3) for potassium and rubidium, respectively, corresponding to a mean interatomic separation of 15.8 mu m or 3.0 x 10(5) a(0) for potassium and 6.1 mu m or 1.2 x 10(5) a(0) for rubidium, where a(0) is the Bohr radius. The experimental results confirm the long range nature of the dipole-dipole interaction, which is critical for understanding many-body physics in atoms/molecules. The long range interaction also has implications in atom-based applications involving many-body interactions. Additionally, we demonstrated that double-quantum 2DCS is sufficiently sensitive to probe dipole-dipole interaction at densities that can be achieved with cold atom in a magneto-optical trap, paving the way for double-quantum 2DCS studies of cold atoms and molecules. The method can also open a new avenue to study long-range interactions in solid state systems such as quantum dots and color centers in diamonds. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement