Efficient production of ultracold polar molecules^(23)Na^(40)K in their absolute ground state via intermediate state of the coupled complex B^(1)Π|ν=4〉^(c)^(3)Σ^(+)|ν=25〉

We report on the efficient creation of a sample of 2.2×10^(4)fermionic polar molecules^(23)Na^(40)K in their rovibrational ground state X^(1)∑^(+)|v=0,J=0>at 247 nK via an intermediate state of the spin-orbit coupled complex B^(1)Π|v=4〉~C^(3)∑^(+)|v=25〉.Compared with the intermediate state of the coupled complex B^(1)Π|v=12〉^(c)^(3)∑^(+)|v=35〉,this intermediate state has the larger Franck-Condon factors for up-and down-leg coupling of stimulated Raman adiabatic passage(STIRAP).We demonstrate this two-photon pathway to the^(23)Na^(40)K ground state molecules and find that the one-way STIRAP transfer efficiency reaches75%.The molecules^(23)Na^(40)K in their rovibrational ground state are an ideal candidate for the quantum simulation and quantum information of ultracold molecules with long-range interaction.