1. Progress on Light Scattering From Degenerate Fermions Seth A. M. Aubin University of Toronto / Thywissen Group May 20, 2006 DAMOP 2006 Work supported by NSERC, CFI, OIT, PRO and Research Corporation.

2. Outline  Motivation  Apparatus  Light Scattering: Simple approach  Light Scattering: next generationOutline  Motivation  Apparatus  Light Scattering: Simple approach  Light Scattering: next generation

3. Light Scattering with Fermions Objective: Modify the lifetime/linewidth of an excited state with quantum statistics.Objective: Motivation:  Trapping environment reduces the number of recoil states  lifetime increases.  Analogous phenomena observed in cavity QED systems.  Similar phenomena frequently observed in condensed matter systems. See for example, A. Högele et al., Appl. Phys. Lett. 86, 221905 2005).Motivation:  Trapping environment reduces the number of recoil states  lifetime increases.  Analogous phenomena observed in cavity QED systems.  Similar phenomena frequently observed in condensed matter systems. See for example, A. Högele et al., Appl. Phys. Lett. 86, 221905 2005).

4. Rb + K

6. Signatures of Degeneracy 87 Rb Bose-Einstein Condensate: 10 4 - 10 5 atoms EFEF kT Rb /E F E K,release /E F Observation of Pauli Pressure Optical Density 0200400 Radial distance (  m) Fermi-Dirac Statistics Boltzmann Statistics Fermion ( 40 K) momentum distribution 0.1T F with 4  10 4 40 K atoms S. Aubin et al., Nature Physics (2006).

7. Signatures of Degeneracy 87 Rb Bose-Einstein Condensate: 10 4 - 10 5 atoms Fermion ( 40 K) momentum distribution EFEF kT Rb /E F E K,release /E F Observation of Pauli Pressure Fit Residuals 0200400 Radial distance (  m) Fermi-Dirac Statistics Boltzmann Statistics 0.1T F with 4  10 4 40 K atoms S. Aubin et al., Nature Physics (2006).

8. Light Scattering with Fermions: Simple Approach Degenerate Fermions: Pauli Blocking of light scattering  Fermi sea reduces number of states an excited atom can recoil into.  Atomic lifetime increases, linewidth decreases. B. DeMarco and D. Jin, Phys. Rev. A 58, R4267 (1998). Th. Busch et al., Europhys. Lett. 44, 755 (1998). Degenerate Fermions: Pauli Blocking of light scattering  Fermi sea reduces number of states an excited atom can recoil into.  Atomic lifetime increases, linewidth decreases. B. DeMarco and D. Jin, Phys. Rev. A 58, R4267 (1998). Th. Busch et al., Europhys. Lett. 44, 755 (1998). kFkF Probe Laser DFG E recoil = 0.4  K E Fermi = 1.1  K

9. Further difficulty with Fermions kxkx kxkx k rec oil Fermi Sea We want this process kxkx kxkx k rec oil Fermi Sea More likely process  Almost no Pauli blocking.

10. Solution ? IDEA: different states can have different Fermi energies/momentum (i.e. different populations), but still be in thermal equilibrium. kxkx kxkx Fermi Sea DFG, m f =7/2 k recoil Non-DFG, m f =9/2  Excite m f = 7/2 atoms.  Look for Pauli blocking of decay into m f = 9/2.

11. How well does it work ? E F,2 = 4E recoil E F,2 = 6E recoil E F,2 = 8E recoil M, suppresion factor Suppression factor: E F,1 E F,2 Theory for a spherical harmonic trap, based on: B. DeMarco and D. Jin, Phys. Rev. A 58, R4267 (1998). Th. Busch et al., Europhys. Lett. 44, 755 (1998). T=0

12. Implementation F = 9/2 9/2 7/2 5/2 9/2 7/2 5/2 11/2 F = 11/2 DFG Non- DFG Procedure:  State preparation: prepare DFG in m f =7/2, and non-DFG in m f =9/2.  Apply weak excitation pulse (atom scatters less than 1 photon). Measure population ratios  Measure population ratios.  Look for a change in ratio as T is decreased.

13. Potential Difficulties Rescattering  Rescattering of scattered light.  far off resonance probe Unwanted transitions  Unwanted transitions to unsuppressed levels.  dipole trap + large Zeeman splittings Heating  Heating due to probe.  short pulse Rescattering  Rescattering of scattered light.  far off resonance probe Unwanted transitions  Unwanted transitions to unsuppressed levels.  dipole trap + large Zeeman splittings Heating  Heating due to probe.  short pulse

14. Dipole Trap Currently installing a 1064 nm dipole trap:  Aligned with Z-wire trap.  It works!  ~100% loading efficiency with 87 Rb. Currently installing a 1064 nm dipole trap:  Aligned with Z-wire trap.  It works!  ~100% loading efficiency with 87 Rb. Loading into the optical trap: 10 5 87 Rb atoms at ~ 1 µK

15. Summary Bose-Fermi mixture  Degenerate Bose-Fermi mixture on a chip. fermions  New scheme for light scattering with fermions. Dipole trap  Dipole trap installed. Fermi Sea k recoil EFEF

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

17. Atom Chip for Bose-Fermi mixtures Advantages:  Short experimental cycle (5-40 s).  Single UHV chamber.  Complex multi-trap geometries.  On-chip RF and B-field sources. Advantages:  Short experimental cycle (5-40 s).  Single UHV chamber.  Complex multi-trap geometries.  On-chip RF and B-field sources. Trap Potential: Z-wire trap Trap Potential: Z-wire trap Chip by J. Esteve, Orsay.

18. Simple Version F = 9/2 9/2 7/2 5/2 9/2 7/2 5/2 11/2 F = 11/2 empty DFG Procedure:  State preparation: prepare DFG in m f =9/2, and nothing in m f =7/2.  Apply weak excitation pulse to in- trap atoms. (atom scatters less than 1 photon)  Use Stern-Gerlach to image the states separately.  Measure population ratios.  Look for a change in ratio as T is decreased.

19. Cross-Section plot

20. Implementation #2 F = 9/2 9/2 7/2 5/2 9/2 7/2 5/2 11/2 F = 11/2 DFG Non- DFG Procedure:  State preparation: prepare DFG in m f =9/2, and non-DFG in m f =7/2.  Apply 2-photon excitation pulse (1 RF + 1 optical).  Look for a decrease in scattering rate as T is decreased. 9/2 7/2 5/2 F = 9/2

21. Sympathetical Cooling Rb-K cross-section (nm 2 )