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.

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

Experimental Sequence MOT Molasses Quadrupole magnetic trap Magnetic transport to chip Load Z-wire magnetic trap RF evaporation to quantum degeneracy

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.

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

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

“Dimples” Take a closer look:

BEC of 87Rb Surprise! Reach Tc with only a 30x loss in number. …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)

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

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:

Outlook Summary: 2 elements trapped simultaneously on a chip. Cold boson-fermion mixture in a micro-magnetic trap. Very efficient evaporation. 2x105 87Rb BEC. 10-20 s production duty cycle. Future: Fermi-degeneracy of 40K. Fabrication of next-generation chip Experiments.

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