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Towards ultra-cold Bose-Fermi mixtures in a micro-magnetic trap

Towards ultra-cold Bose-Fermi mixtures in a micro-magnetic trap. Seth Aubin University of Toronto / Thywissen Group. Work supported by NSERC, CFI, OIT, and Research Corporation. Objectives: Condensed matter simulations. Boson-fermion mixtures. Atom interferometry. Advantages:

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Towards ultra-cold Bose-Fermi mixtures in a micro-magnetic trap

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  1. Towards ultra-cold Bose-Fermi mixtures in a micro-magnetic trap Seth Aubin University of Toronto / Thywissen Group Work supported by NSERC, CFI, OIT, and Research Corporation.

  2. Objectives: • Condensed matter simulations. • Boson-fermion mixtures. • Atom interferometry. • Advantages: • Short experimental cycle. • Single UHV chamber. • Complex multi-trap geometries. Why ultra-cold bosons and fermions? Why on a chip?

  3. Experimental Sequence • Experimental sequence: • MOT • Molasses • Quadrupole magnetic trap • Magnetic transport to chip • Load Z-wire magnetic trap • RF evaporation to quantum degeneracy

  4. Light-Induced Atom Desorption (LIAD) • Conflicting pressure requirements: • Large Alkali partial pressure  large MOT. • UHV vacuum  long magnetic trap lifetime. Solution: Use LIAD to control pressure dynamically ! • 405nm LEDs (power=170 mW) in a pyrex cell.

  5. Iz Atom Chip • Technology: • Electroplated gold wires on a silicon substrate. • Manufactured by J. Estève (Aspect/Orsay). Trap Potential: Z-wire trap Theory rf for evaporation

  6. Extra compression at low temperature? T=19 K T=7 K faxial boosted by two (to 26 Hz)

  7. “Dimples” Take a closer look:

  8. BEC of 87Rb …Continue evaporation: @1.740 MHz: N = 7.3x105, T>Tc @1.725 MHz: N = 6.4x105, T~Tc @1.660 MHz: N=1.4x105, T<Tc Surprise! Reach Tc with only a 30x loss in number. (trap loaded with 2x107 atoms)

  9. High Evaporation Efficiency MOT & Molasses Chip Loading Magnetic Trap Transfer to Chip RF Evaporation 0.26 s 5-12 s 1.10 s 2.50 s • Log slope efficiency: • BEC of up to 2x105 atoms. • Cycle times as short as 10 seconds.

  10. 87Rb - 40K Bose-Fermi Mixture on a Chip Simultaneously, we have loaded up to 1.5x107 87Rb atoms. 4x104 40K atoms How to see dilute fermions? 1D chip “MOT” fluorescence detection:

  11. Outlook • Summary: • 2 elements trapped simultaneously on a chip. • Cold boson-fermion mixture in a micro-magnetic trap. • Very efficient evaporation. • 2x10587Rb BEC. • 10-20 s production duty cycle. • Future: • Fermi-degeneracy of 40K. • Fabrication of next-generation chip • Experiments.

  12. Colors: Staff/Faculty Postdoc Grad Student Undergraduate S. Myrskog S. Aubin L. J. LeBlanc I. Leroux M. H. T. Extavour A. Stummer B. Cieslak D. Shirokoff J. H. Thywissen D. McKay Thywissen Group

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