We present measurements of interspecies Feshbach resonances and subsequent creation of dualspecies Bose-Einstein condensates of 23 Na and 39 K. We prepare both optically trapped ensembles in the spin state |f = 1, m f = −1 and perform atom loss spectroscopy in a magnetic field range from 0 to 700 G. The observed features include several s-wave poles and a zero crossing of the interspecies scattering length as well as inelastic two-body contributions in the M = mNa+mK = −2 submanifold. We identify and discuss the suitability of different magnetic field regions for the purposes of sympathetic cooling of 39 K and achieving dual-species degeneracy. Two condensates are created simultaneously by evaporation at a magnetic field of about 150 G, which provides sizable intra-and interspecies scattering rates needed for fast thermalization. The impact of the differential gravitational sag on the miscibility criterion for the mixture is discussed. Our results serve as a promising starting point for the magnetoassociation into quantum degenerate 23 Na 39 K Feshbach molecules.arXiv:1709.03796v2 [cond-mat.quant-gas]

We explore possible pathways for the creation of ultracold polar NaK molecules in their absolute electronic and rovibrational ground state starting from ultracold Feshbach molecules. In particular, we present a multi-channel analysis of the electronic ground and K(4p)+Na(3s) excited state manifold of NaK, analyze the spin character of both the Feshbach molecular state and the electronically excited intermediate states and discuss possible coherent two-photon transfer paths from Feshbach molecules to rovibronic ground state molecules. The theoretical study is complemented by the demonstration of STIRAP transfer from the X 1 Σ + (v=0) state to the a 3 Σ + manifold on a molecular beam experiment.

In this paper, we present an electrode geometry for the manipulation of ultracold, rovibrational ground state NaK molecules. The electrode system allows to induce a dipole moment in trapped diatomic NaK molecules with a magnitude up to 68% of their internal dipole moment along any direction in a given two-dimensional plane. The strength, the sign and the direction of the induced dipole moment is therefore fully tunable. The maximal relative variation of the electric field over the trapping volume is below 10 −6 . At the desired electric field value of 10 kV cm −1 this corresponds to a deviation of 0.01 V cm −1 . Furthermore, the possibility to create strong electric field gradients provides the opportunity to address molecules in single layers of an optical lattice. The electrode structure is made of transparent indium tin oxide and combines large optical access for sophisticated optical dipole traps and optical lattice configurations with the possibility to create versatile electric field configurations.

We present a detailed study of interspecies Feshbach resonances of the bosonic 23 Na+ 39 K mixture for magnetic fields up to 750 G in various collision channels. A total of fourteen Feshbach resonances are reported, as well as four zero crossings of the scattering length and three inelastic two-body loss features. We use the observed magnetic field locations of the resonant features together with the known data on 23 Na+ 40 K to refine the singlet and triplet ground state potentials of NaK and achieve a consistent description of Feshbach resonances for both, the Bose-Bose mixture of 23 Na+ 39 K as well as the Bose-Fermi mixture of 23 Na+ 40 K. We also discuss the influence of the interplay between inelastic two-body and three-body processes on the observation of a Feshbach resonance.

In this paper, we present a high-resolution, simple, and versatile imaging system for single-site resolved imaging of atoms in optical lattices. The system, which relies on an adaptable infinite conjugate two-lens design, has a numerical aperture of 0.52, which can in the ideal case be further extended to 0.57. It is optimized for imaging on the sodium D2-line but allows us to tune the objective’s diffraction limited performance between 400 nm and 1000 nm by changing the distance between the two lenses. Furthermore, the objective is designed to be integrated into a typical atomic physics vacuum apparatus where the operating distance can be large (>20 mm) and diffraction limited performance still needs to be achieved when imaging through thick vacuum windows (6 mm to 10 mm). Imaging gold nanoparticles, using a wavelength of 589 nm which corresponds to the D2-line of sodium atoms, we measure diffraction limited performance and a resolution corresponding to an Airy radius of less than 0.7 µm, enabling potential single-site resolution in the commonly used 532 nm optical lattice spacing.