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

3. Experimental Sequence Experimental sequence: 1.MOT 2.Molasses 3.Quadrupole magnetic trap 4.Magnetic transport to chip 5.Load Z-wire magnetic trap 6.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. Atom Chip Technology: Electroplated gold wires on a silicon substrate. Manufactured by J. Estève (Aspect/Orsay). Trap Potential: Z-wire trap Theory IzIz rf for evaporation

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

7. “Dimples” Take a closer look:

8. BEC of 87 Rb @1.725 MHz: N = 6.4x10 5, T~T c @1.660 MHz: N=1.4x10 5, T<T c @1.740 MHz: N = 7.3x10 5, T>T c Surprise! Reach T c with only a 30x loss in number. …Continue evaporation: (trap loaded with 2x10 7 atoms)

9. High Evaporation Efficiency MOT & Molasses Magnetic Trap Transfer to Chip Chip Loading RF Evaporation 5-12 s1.10 s 0.26 s 2.50 s BEC of up to 2x10 5 atoms. Cycle times as short as 10 seconds. Log slope efficiency:

10. 87 Rb - 40 K Bose-Fermi Mixture on a Chip Simultaneously, we have loaded up to 1.5x10 7 87 Rb atoms. 4x10 4 40 K 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. 2x10 5 87 Rb BEC. 10-20 s production duty cycle. Future: Fermi-degeneracy of 40 K. Fabrication of next-generation chip Experiments.

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