Singlet Pathway to the Ground State of Ultracold Polar Molecules

• Published in: arXiv.org 2019-08
• Main Authors: Yang, Anbang, Botsi, Sofia, Kumar, Sunil, Pal, Sambit B, Lam, Mark M, Čepaitė, Ieva, Laugharn, Andrew, Dieckmann, Kai
• Format: Article
• Language: English
• Subjects: Coupling (molecular); Ground state; Hyperfine structure
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1908.02703

Starting from weakly bound Feshbach molecules, we demonstrate a two-photon pathway to the dipolar ground state of bi-alkali molecules that involves only singlet-to-singlet optical transitions. This pathway eliminates the search for a suitable intermediate state with sufficient singlet-triplet mixing and the exploration of its hyperfine structure, as is typical for pathways starting from triplet dominated Feshbach molecules. By selecting a Feshbach state with a stretched singlet hyperfine component and controlling the polarization of the excitation laser, we assure coupling to only a single hyperfine component of the \(\textrm{A}^{1}\Sigma^{+}\) excited potential, even if the hyperfine structure is not resolved. Similarly, we address a stretched hyperfine component of the \(\textrm{X}^{1}\Sigma^{+}\) rovibrational ground state, and therefore an ideal three level system is established. We demonstrate this pathway with \({}^{6}\textrm{Li}{}^{40}\textrm{K}\) molecules. By exploring deeply bound states of the \(\textrm{A}^{1}\Sigma^{+}\) potential, we are able to obtain large and balanced Rabi frequencies for both transitions. This method can be applied to other molecular species.