Laser-assisted binding of ultracold polar molecules with Rydberg atoms in the van der Waals regime

TL;DR

This paper investigates laser-assisted formation of long-range bound states between ultracold molecules and Rydberg atoms, revealing efficient photoassociation and predicting binding energies and formation rates in dilute ultracold gases.

Contribution

It introduces a two-photon photoassociation scheme for forming ultralong-range trimers of molecules and Rydberg atoms, expanding understanding of ultracold long-range interactions.

Findings

Efficient two-photon photoassociation over broad Rydberg channels.

Predicted binding energies of 10-1000 kHz for vibrational states.

Trimer formation rate around 10^8 s^{-1} at 1 μK.

Abstract

We study ultracold long-range collisions of heteronuclear alkali-metal dimers with a reservoir gas of alkali-metal Rydberg atoms in a two-photon laser excitation scheme. In a low density regime where molecules remain outside the Rydberg orbits of the reservoir atoms, we show that the two-photon photoassociation (PA) of the atom-molecule pair into a long-range bound trimer state is efficient over a broad range of atomic Rydberg channels. As a case study, we obtain the PA lineshapes for the formation of trimers composed of KRb molecules in the rovibrational ground state and excited Rb atoms in the asymptotic Rydberg levels $n^{2}S_j$ and $n^{2}D_j$, for $n=20-80$. We predict atom-molecule binding energies in the range $10-10^3$ kHz for the first vibrational state below threshold. The average trimer formation rate is order $10^8\, {\rm s}^{-1}$ at 1.0 $\mu$K, and depends weakly on the principal quantum number $n$. Our results set the foundations for a broader understanding of exotic long range collisions of dilute molecules in ultracold atomic Rydberg reservoirs.