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AtMol Home IQ3 Department of Physics Durham University
RbCs: ultracold atomic mixtures and molecules.
D.J. McCarron, D.L. Jenkin, M. Köppinger, H-W. Cho, S.A. Hopkins & S.L. Cornish
Funding:
"A Quantum Gas of Ultracold Polar Molecules" EPSRC EP/H003363/1. (May 2010 - Apr 2014)
"Quantum-degenerate dipolar gases of bialkali molecules" EPSRC EP/E041604/1, part of a EuroQUAM Collaborative Research Project. (Sep 2007 - Sep 2011)
"A Two-Species Mixture of Quantum Degenerate Bose Gases" EPSRC GR/S78339/01. (Oct 2004 - Sep 2007)
Outline:
The last decade has witnessed an explosion of activity in the field of quantum degenerate gases. Experimental and theoretical activity within the field continues to progress at a remarkable rate as existing techniques are extended and combined in ever richer systems. At present it is possible to identify several "hot topics" which form the basis for research in this field including:
  • The use of Feshbach resonances both to control the interactions within a quantum degenerate gas and as a means to produce ultracold molecules.
    		•
  • The realization of mixtures of two different quantum degenerate atomic gases.
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  • The study of quantum degenerate gases in optical lattice potentials and their applications to quantum computation and condensed matter.
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    The goal of this project is to produce a two-component quantum degenerate mixture composed of Bose-Einstein condensates of Rb and Cs in a highly adjustable optical trapping potential. This specific combination of atomic species permits the study of all of the "hot topics" listed above.

    Objectives:
    The specific objectives of the project include:
  • The measurement of the interspecies collision properties of the Rb-Cs mixture in the lower hyperfine ground states.
  • The location and identification of interspecies Feshbach resonances.
  • The investigation of sympethetic cooling of Cs to quantum degeneracy.
  • The study of the miscibility and stability of a two-species quantum degenerate mixture.
  • The transfer of the mixture into a 3D optical lattice and the study of the two species Mott insulator transition.
    • These objectives represent the first step towards the long-term project goal, namely the creation of ultracold heteronuclear ground state molecules and the study of dipolar quantum gases.

    Highlights:
    Research highlights over recent years include:
  • 18/12/09 - First demonstration of optically trapped 133Cs.
  • 06/03/10 - 87Rb BEC in a single beam hybrid trap.
  • 07/05/10 - 87Rb BEC in the levitated crossed dipole trap.
  • 09/06/10 - 133Cs BEC in the levitated crossed dipole trap.
  • 08/07/10 - Dual-species BEC realised in the same trapping potential.
  • 27/08/10 - Magneto-association of Cs2 Feshbach molecules across a resonance at 19.8 G.
  • 03/09/10 - Interspecies Feshbach resonance observed at 181.7 G.
  • 05/06/11 - 133Cs BEC realised in new bias field regime between 18 G and 19.6 G.
    • Latest poster:        Latest results:
    May 2011June 2011
    The evaporation of Cs alone in the crossed dipole trap in the F=3, mF=+3 state was investigated for bias fields between 5G and 45G. For each bias field the levitated crossed dipole trap depth was reduced from 69 µK to 1.9 µK in 2.6 seconds. The remaining atom number and temperature were used to calculate the final phase-space density in the trap and the efficiency of the evaporation. The results of this investigation are shown in the figure and agree very well with expected results using the theoretical scattering length data provided by P. Julienne and co-works at NIST (bottom plot).

    We have located two regions where the evaporation efficiency ~3 (purple dashed boxes), here subsequent evaporation by titling the trap with the magnetic field gradient can lead to the production of 133Cs condensates containing up 8x104 atoms. One region is the standard window used to produce 133Cs BEC located between 20-25G. The second window spans 18G to 19.6G and marks the discovery of a new bias field region where Cs BEC can be achieved.


    Updated by Simon L. Cornish, May 2010
    Department of Physics, Durham University Tel +44 (0)191 33 43520
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