Formation of ultracold NaRb Feshbach molecules

Abstract

We report the creation of ultracold bosonic 23 Na 87 Rb Feshbach molecules via magneto-association. By ramping the magnetic field across an interspecies Feshbach resonance (FR), at least 4000 molecules can be produced out of the near degenerate ultracold mixture. Fast loss due to inelastic atom-molecule collisions is observed, which limits the pure molecule number, after residual atoms removal, to 1700. The pure molecule sample can live for 21.8(8) ms in the optical trap, long enough for future molecular spectroscopy studies toward coherently transferring to the singlet ro-vibrational ground state, where these molecules are stable against chemical reaction and have a permanent electric dipole moment of 3.3 Debye. We have also measured the Feshbach molecule's binding energy near the FR by the oscillating magnetic field method and found these molecules have a large closed-channel fraction.The creation and manipulation of ultracold heteronuclear molecules have received intensive attentions in recent years due to the versatile and promising potential applications [1, 2] of these molecules. With controllable, anisotropic and long range dipole-dipole interactions, they could be used in quantum computation [3,4], quantum simulation [5], precision measurement [6,7] and controlled cold chemistry [8]. So far, the most successful scheme for producing ultracold ground-state dipolar molecule is by associating ultracold atoms near Feshbach resonances (FRs) [9, 10] to form weakly-bound molecules first, followed by a stimulated Raman adiabatic rapid passage (STIRAP) [11] to transfer them to a deeply bound state [12,13]. This has been successfully applied to the 40 K 87 Rb system [14], where near degenerate ground-state dipolar fermionic molecules are created. However, the chemical reaction 2 KRb→ K 2 + Rb 2 is an exoergic process which results in a large inelastic loss, severely limiting the trap lifetime of the KRb molecular gas [15][16][17].Currently, there is a great effort in generalizing the KRb production scheme to other heteronuclear alkali dimers. Creation of Feshbach molecules of RbCs [18], LiNa [19] and NaK [20] were already reported in 2012, and very recently ground-state RbCs molecules were successfully produced [21,22]. In this work, we focus on the bosonic NaRb molecule, which in the absolute ground state is stable against chemical reactions [23] and has a permanent electric dipole moment as large as 3.3 Debye [24]. The ground-state NaRb molecule can be readily polarized with a moderate electric field. For instance, at 5 kV cm −1 the induced dipole moment is already more than 2 Debye. Therefore, it is an appealing system for studying the bosonic quantum gas with strong dipolar interactions. Recently, the double species Bose-Einstein condensates (BECs) of 23 Na and 87 Rb atoms have been produced [25] and their interspecies FRs [26] were also investigated in our group. One of the s-wave resonances between atoms in their lowest hyperfine Zeeman state locates conveniently at a magnetic field B 0 = 347.7 G with a width ...

Collisions of ultracold 23 Na 87 Rb molecules with controlled chemical reactivities

“…The starting point of our experiment is an optically trapped sample of weakly-bound NaRb Feshbach molecules (FMs) (25). To study and compare the collisions in Eqs.…”

Microscopic derivation of multichannel Hubbard models for ultracold nonreactive molecules in an optical lattice

“…Similar indirect molecule-production experiments have been successfully performed for the molecules RbCs [43][44][45][46][47][48], NaK [49][50][51][52], and NaRb [53,54]. Unlike KRb, these are expected to be nonreactive.…”

Long-range states of the NaRb molecule near theNa(3 2S1/2)+Rb(5 Zhu1, Li2, He3 et al. 2016Phys. Rev. ASelf Cite110110View full textAdd to dashboardCite

“…The final magnetic field is at 340 G, where the molecules have a binding energy of 2π×12 MHz and about 80% closed channel fraction. The trap lifetime of the pure molecule sample is more than 20 ms [21].…”

“…Our Feshbach molecule is s-wave in nature; thus its pure rotation is l = 0. It is electronic spin triplet dominated with the second to the last vibrational level (v = −2) of the a 3 Σ + state as the closed channel [21]. The total electronic angular momentum is thus j = 1.…”

“…In the past two years, we have prepared an ultracold mixture of 23 Na and 87 Rb [19] and studied their Feshbach resonances [20]. Recently, we have successfully produced 23 Na 87 Rb Fesh-bach molecules by sweeping the magnetic field across a Feshbach resonance [21]. The next critical step for making ground-state 23 Na 87 Rb molecules is to find a path for an efficient stimulated Raman process.…”