Ultracold Dipolar Gas of Fermionic $^{23}$Na$^{40}$K Molecules in their Absolute Ground State

TL;DR

This paper reports the creation of a stable, ultracold fermionic NaK molecule gas in its absolute ground state with induced electric dipole moments, enabling studies of many-body physics with strongly dipolar Fermi gases.

Contribution

It demonstrates the coherent transfer of weakly bound molecules into the absolute ground state and measures the resulting gas's stability and dipole moment.

Findings

Molecular gas lifetime exceeds 2.5 seconds

Induced dipole moment up to 0.8 Debye

Successful two-photon transfer into ground state

Abstract

We report on the creation of an ultracold dipolar gas of fermionic $^{23}$Na$^{40}$K molecules in their absolute rovibrational and hyperfine ground state. Starting from weakly bound Feshbach molecules, we demonstrate hyperfine resolved two-photon transfer into the singlet ${\rm X}^1\Sigma^+ |v{=}0,J{=}0\rangle$ ground state, coherently bridging a binding energy difference of 0.65 eV via stimulated rapid adiabatic passage. The spin-polarized, nearly quantum degenerate molecular gas displays a lifetime longer than 2.5 s, highlighting NaK's stability against two-body chemical reactions. A homogeneous electric field is applied to induce a dipole moment of up to 0.8 Debye. With these advances, the exploration of many-body physics with strongly dipolar Fermi gases of $^{23}$Na$^{40}$K molecules is in experimental reach.