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

Abstract

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 $4.81\times 10^8$ cm${}^{-3}$ and $8.40\times 10^9$ cm${}^{-3}$ for potassium and rubidium, respectively, corresponding to a mean interatomic separation of 15.8 $\hat{I}¼$m or $3.0\times 10^5{a}_0$ for potassium and 6.1 $\hat{I}¼$m or $1.2\times 10^5{a}_0$ for rubidium, where $a_0$ is the Bohr radius. We report the lowest atomic density at which dipole-dipole interactions are detected. 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 states systems such as quantum dots and color centers in diamonds.

5 pages, 4 figures