Two-Photon Pathway to Ultracold Ground State Molecules of ${}^{23}$Na${}^{40}$K

Abstract

We report on high-resolution spectroscopy of ultracold fermionic \nak~Feshbach molecules, and identify a two-photon pathway to the rovibrational singlet ground state via a resonantly mixed \Bcres intermediate state. Photoassociation in a ${}^{23}$Na-${}^{40}$K atomic mixture and one-photon spectroscopy on \nak~Feshbach molecules reveal about 20 vibrational levels of the electronically excited \ctrip state. Two of these levels are found to be strongly perturbed by nearby \Bsing states via spin-orbit coupling, resulting in additional lines of dominant singlet character in the perturbed complex {${\mathrm{B}}^1\Pi |v=4⟩\sim {\mathrm{c}}^3{\Sigma }^{+}|v=25⟩$}, or of resonantly mixed character in {${\mathrm{B}}^1\Pi |v=12⟩\sim {\mathrm{c}}^3{\Sigma }^{+}|v=35⟩$}. The dominantly singlet level is used to locate the absolute rovibrational singlet ground state ${\mathrm{X}}^1{\Sigma }^{+}|v=0,J=0⟩$ via Autler-Townes spectroscopy. We demonstrate coherent two-photon coupling via dark state spectroscopy between the predominantly triplet Feshbach molecular state and the singlet ground state. Its binding energy is measured to be 5212.0447(1) \cm, a thousand-fold improvement in accuracy compared to previous determinations. In their absolute singlet ground state, \nak~molecules are chemically stable under binary collisions and possess a large electric dipole moment of $2.72$ Debye. Our work thus paves the way towards the creation of strongly dipolar Fermi gases of NaK molecules.

23 pages, 8 figures

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• Clean Floquet Time Crystals: Models and Realizations in Cold Atoms
• Second-Scale Nuclear Spin Coherence Time of Trapped Ultracold ${}^{23}$Na${}^{40}$K Molecules
• Modeling the adiabatic creation of ultracold, polar ${}^{23}\mathrm{N}{\mathrm{a}}^{40}\mathrm{K}$ molecules
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• Coherent Microwave Control of Ultracold ${}^{23}$Na${}^{40}$K Molecules
• Resonant dipolar collisions of ultracold molecules induced by microwave dressing
• Magnetic Feshbach resonances in collisions of ${}^{23}$Na${}^{40}$K with ${}^{40}$K
• Observation of interference between resonant and detuned STIRAP in the adiabatic creation of ${}^{23}$Na${}^{40}$K molecules
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• Ultracold nonreactive molecules in an optical lattice: connecting chemistry to many-body physics
• Efficient conversion of closed-channel dominated Feshbach molecules of ${}^{23}$Na${}^{40}$K to their absolute ground state
• Feshbach resonances and weakly bound molecular states of boson-boson and boson-fermion NaK pairs
• Singlet Pathway to the Ground State of Ultracold Polar Molecules
• Resonant control of elastic collisions between ${}^{23}$Na${}^{40}$K molecules and ${}^{40}$K atoms
• Two-Photon Spectroscopy of the NaLi Triplet Ground State
• Microscopic derivation of multi-channel Hubbard models for ultracold nonreactive molecules in an optical lattice
• Transition strength measurements to guide magic wavelength selection in optically trapped molecules
• Lattice model parameters for ultracold nonreactive molecules: chaotic scattering and its limitations
• Efficient Pathway to NaCs Ground State Molecules
• Interaction-driven Lifshitz transition with dipolar fermions in optical lattices
• Fast, precise, and widely tunable frequency control of an optical parametric oscillator referenced to a frequency comb
• Time-of-flight expansion of trapped dipolar Fermi gases: From the collisionless to the hydrodynamic regime
• Pendular trapping conditions for ultracold polar molecules enforced by external electric fields
• Competing many-body instabilities in two-dimensional dipolar Fermi gases
• Bosonic molecules in a lattice: unusual fluid phase from multichannel interactions
• Stability of quantum degenerate Fermi gases of tilted polar molecules
• Fractional quantum Hall states of dipolar fermions in a strained optical lattice
• Empirical LiK excited state potentials: connecting short range and near dissociation expansions
• Asymptotic behavior of correlation functions of one-dimensional polar-molecules on optical lattices