We report the creation of ultracold samples of 39K133Cs molecules in their rovibrational groundstate. By investigating potentially suitable excited states using one- and two-photon spectroscopy,we have identified a pathway to the ground state via an exceptionally narrow intermediate state.Using Stimulated Raman Adiabatic Passage (STIRAP), we create trapped samples of up to 3500molecules at temperatures of 1 μK with one-way efficiencies of 71%. The lifetime of these samplesis limited by a near-universal two-body loss process, which could shed new light on similar lossmechanisms in other molecular species. Our results are a step towards establishing an alternativeplatform for the study of bosonic and fermionic quantum matter with strong dipolar interactions.

We acknowledge funding from the European Research Council (ERC) under Project No. 789017, the FWF under Project No. P29602-N36, a Wittgenstein prize grant under FWF Project No. Z336-N36, an FFG infrastructure grant with project number FO999896041 and by the FWF’s COE 1 and quantA. K.P.Z. acknowledges support from the Austrian Science Fund (FWF) within the DK-ALM (Grant No. W1259- N27).This research was funded in whole or in part by the Austrian Science Fund (FWF) Grant DOI 10.55776/W1259. For open access purposes, the authors have applied a CC BY public copyright license to any author-accepted manuscript version arising from this submission.

Compared to version 1: x-axis in Fig. 3 (a) and (b) is now reversed, and as a result the content of (a) and (b) is swapped.