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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: - PowerPoint PPT Presentation
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Towards ultra-cold Bose-Fermi mixturesTowards ultra-cold Bose-Fermi mixturesin a micro-magnetic trapin 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?
Advantages:
• Short experimental cycle.
• Single UHV chamber.
• Complex multi-trap geometries.
Why on a chip?
Objectives:
• Condensed matter simulations.
• Boson-fermion mixtures.
• Atom interferometry.
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
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
Theory Iz
rf for evaporation
T=19 K
T=7 K
faxial boosted by two (to 26 Hz)
kTrUrn )(exp)( 31
Extra compression at low temperature?
“Dimples”
Take a closer look:
BEC of 87Rb
@1.725 MHz:N = 6.4x105, T~Tc
@1.660 MHz:N=1.4x105, T<Tc
@1.740 MHz:N = 7.3x105, T>Tc
Surprise! Reach Tc with only a 30x loss in number.
…Continue evaporation:
(trap loaded with 2x107 atoms)
High Evaporation EfficiencyMOT &Molasses
Magnetic TrapTransfer to Chip
ChipLoading RF Evaporation
5-12 s 1.10 s 0.26 s 2.50 s
• BEC of up to 2x105 atoms.
• Cycle times as short as 10 seconds.
• Log slope efficiency:
log()
log(N)4.0
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:
OutlookSummary:
• 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 GroupThywissen Group
J. H. Thywissen
S. Aubin M. H. T. Extavour
A. StummerS. Myrskog
L. J. LeBlanc
D. McKay
B. Cieslak
D. Shirokoff
Staff/FacultyPostdocGrad StudentUndergraduate
Colors:
I. Leroux