Interspecies thermalization in an ultracold mixture of Cs and Yb in an optical trap

Abstract

We present measurements of interspecies thermalization between ultracold samples of 133 Cs and either 174 Yb or 170 Yb. The two species are trapped in a far-off-resonance optical dipole trap and 133 Cs is sympathetically cooled by Yb. We extract effective interspecies thermalization cross sections by fitting the thermalization measurements to a kinetic model, giving σ Cs 174 Yb = (5 ± 2) × 10 −13 cm 2 and σ Cs 170 Yb = (18 ± 8) × 10 −13 cm 2 . We perform quantum scattering calculations of the thermalization cross sections and optimize the CsYb interaction potential to reproduce the measurements. We predict scattering lengths for all isotopic combinations of Cs and Yb. We also demonstrate the independent production of 174 Yb and 133 Cs Bose-Einstein condensates using the same optical dipole trap, an important step towards the realization of a quantum-degenerate mixture of the two species.The realization of ultracold atomic mixtures [1][2][3][4][5][6][7][8][9][10][11][12] has opened up the possibility of exploring new regimes of few-and many-body physics. Such mixtures have been used to study Efimov physics [13][14][15], probe impurities in Bose gases [16], and entropically cool gases confined in an optical lattice [17]. Pairs of atoms in the mixtures can be combined using magnetically or optically tunable Feshbach resonances to create ultracold molecules [18][19][20][21][22][23][24][25][26]. These ultracold molecules have a wealth of applications, such as tests of fundamental physics [27][28][29], realization of novel phase transitions [30][31][32], and the study of ultracold chemistry [33,34]. In addition, the long-range dipole-dipole interactions present between pairs of polar molecules make them useful in the study of dipolar quantum matter [35,36] and ultracold molecules confined in an optical lattice can simulate a variety of condensedmatter systems [37][38][39].Although the large majority of work on ultracold molecules has focused on bi-alkali systems, there is burgeoning interest in pairing alkali-metal atoms with divalent atoms such as Yb [40][41][42][43][44][45] or Sr [46]. The heteronuclear 2 Σ molecules formed in these systems have both an electric and a magnetic dipole moment in the ground electronic state. The extra magnetic degree of freedom opens up new possibilities for simulating a range of Hamiltonians for spins interacting on a lattice and for topologically protected quantum information processing [47].One of the challenging aspects of creating molecules in these systems is that the Feshbach resonances tend to be narrow and sparse. They are narrow because the main coupling responsible for them is the weak distance dependence of the alkali-metal hyperfine coupling, caused by the spin-singlet atom at short range [48] [48,49], and for some systems may be at impractically high magnetic fields. Amongst the various alkali-Yb combinations, CsYb has been proposed as the most favorable candidate because the high mass of Cs facilitates a higher density of bound states near threshold and its large hyperfi...

Two-photon photoassociation spectroscopy of CsYb: Ground-state interaction potential and interspecies scattering lengths

“…Mixtures of ultracold atomic gases provide an appealing platform for numerous avenues of research, including the investigation of novel quantum phases [1][2][3][4][5][6][7], the study of Efimov physics [8][9][10][11] and the creation of ultracold polar molecules [12][13][14][15][16][17][18][19][20][21][22]. Early experiments explored bi-alkali-metal gases [23][24][25][26][27][28][29][30][31][32][33], but there is currently a growing interest in mixtures composed of alkali-metal and closed-shell atoms [34][35][36][37][38][39][40][41]. Such mixtures open up the possibility of creating paramagnetic ground-state polar molecules, with applications in quantum simulation and quantum information [42][43][44], precision measurement [45], tests of fundamental physics [46]…”

Production of a degenerate Fermi-Fermi mixture of dysprosium and potassium atoms

“…To determine the cross section for elastic collisions between 161 Dy and 40 K atoms we perform an interspecies thermalization measurement [95][96][97]. We interrupt the evaporation process in the CDT when the power in the horizontal beam reaches 350 mW.…”

Photoassociation of Ultracold CsYb Molecules and Determination of Interspecies Scattering Lengths

“…This is due to its troublesome scattering properties [126,[247][248][249] which prevented groups from achieving a Cs BEC until 2002 [119], some 7 years after the first BECs in alkali atoms were observed [250,251]. Even after the first observation of Cs BEC only a handful of other groups worldwide have reported production of Cs BECs [205,[252][253][254].…”