Ultracold Dipolar Gas of Fermionic Na²³K⁴⁰ Molecules in Their Absolute Ground State

We report on the creation of an ultracold dipolar gas of fermionic Na²³K⁴⁰ 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 X¹Σ⁺|v=0,J=0〉 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 D. With these advances, the exploration of many-body physics with strongly dipolar Fermi gases of Na²³K⁴⁰ molecules is within experimental reach.