Two-photon-assisted collisions in ultracold gases of polar molecules II : Optical shielding of ultracold polar molecular collisions

TL;DR

This paper presents a theoretical study on using two-photon optical shielding to suppress inelastic collisions in ultracold polar molecules, demonstrating conditions that favor elastic collisions and enhance stability.

Contribution

It introduces a novel two-photon laser scheme to control molecular collisions, achieving a significant increase in elastic collision probability in ultracold polar gases.

Findings

Identification of laser parameters that favor elastic over inelastic collisions

Demonstration of a factor of about 2 increase in elastic collision rate

Analysis of scattering resonances linked to laser-induced long-range molecular states

Abstract

We theoretically investigate the collisions between ultracold polar molecules in the presence of two lasers ensuring a Raman resonant transition on individual molecules to suppress photon scattering, taking the example of bosonic $^{23}$Na$^{39}$K molecules. By varying laser detunings and intensities, we enable a repulsive long-range interaction potential between molecules. After solving a set of coupled Schr\"odinger equations with the Hamiltonian written in the basis of laser-dressed states of the molecule pair at infinite distance, we identify quasi-resonant conditions under which elastic collisions are favored over inelastic and reactive ones, by a factor of about 2, thus demonstrating a promising pathway for efficient two-photon optical shielding of ultracold molecular collisions. The results are analyzed in terms of scattering length of the colliding laser-dressed molecules, which exhibit prominent resonances assigned to the interaction of the entrance channel with other specific channels, consistent with the existence of a quasi-bound level of the long-range molecular pair induced by the lasers.