1. An atomic Fermi gas near a p-wave Feshbach resonance
D. Jin
JILA, NIST and the University of Colorado
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$ NSF, NIST

2. Outline Motivation A p-wave Feshbach resonance
Molecule energies and lifetimes
Future
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3. Fermionic superfluidity
Cooper pairing:
two correlated fermions act like a boson
Examples
Fermi condensate
Superconductivity: Cooper pairs
of electrons
Superfluid 3He: 3He atom pairs
Superfluidity in nuclear matter: Nucleon pairs

4. P-wave pairing? Fermi condensates with non-s-wave pairing? Examples:
superfluid 3He (p-wave)
high Tc superconductors (d-wave)
Novel features:
anistropic gap
multiple superfluid phases,
narrow resonance
s-wave
L=0
p-wave
L=1
m l= -1,0,+1

5. Making molecules
This is the first step toward making molecule condensates and fermion pair condensates.
New possibilities: non-s-wave molecules, heteronuclear molecules, fermionic molecules, ground-state molecules, and polar molecules.
Grimm (s- to g- wave), Salomon (p-wave)
other non-s-wave Feshbach molecule studies:
Grimm (s- to g- wave), Salomon (p-wave)

6. Making molecules
Molecules can be very efficiently created using a Feshbach resonance.
magnetic-field sweep across resonance
three-body collisions near a Feshbach resonance
rf association
magnetic-field modulation
Grimm (s- to g- wave), Salomon (p-wave)

7. Feshbach resonance
A magnetic-field tunable atomic scattering resonance
Channels are coupled by the hyperfine interaction.
molecule state in channel 2
→ ←
colliding atoms in channel 1

8. P-wave resonance S V(R) V(R) centrifugal barrier 300 mK 0.5 mK R R
V(R) R
V(R) R
centrifugal barrier
300 mK
0.5 mK
300 K
barrier is 5.8 MHz high = 280 microK. EF is about 0.5 microK = 10 kHz (580 times smaller than barrier); depth of potential is about 350 K

9. Collisions and Fermions
two spin-states
40K
elastic collision
cross section
one spin-state
Add ref
B. DeMarco et al., PRL 82, 4208 (1999)

10. elastic collision cross section
P-wave resonance
40K
elastic collision cross section
spin-polarized gas
|f=9/2, mf=-7/2>
current data, rethermalization time is 23 seconds away from resonance and 0.2 seconds at resonance
C.A. Regal, C. Ticknor, J.L. Bohn, & D.S. Jin, PRL 90, (2003)

11. Multiplet structure ml = 0 ml = ±1 ml = ±1 ml = 0 B B0 = 198.3 G
C. Ticknor, C.A. Regal, D.S. Jin, and J.L. Bohn, PRA 69, (2004).

12. Width of loss feature
ml = 0
resonance
Feature of a narrow resonance

13. B-field modulation
Near a Feshbach resonance, a resonant oscillating B-field
can create molecules.
dissociation M. Greiner, C.A. Regal, & D.S. Jin, PRL 94, (2005)
association S.T. Thompson, E. Hodby, & C.E. Wieman, PRL 94,
(2005)
V(R) R
centrifugal barrier
B below both
resonances
162 mG below m=1 resonance

14. Quasi-bound molecules
V(R)
centrifugal barrier R
162 mG below m=1 resonance
B above the
resonance

15. P-wave molecule energyB
ml = ±1
ml = 0
190 kHz/G
J.P. Gaebler, J.T. Stewart, J.L. Bohn, & D.S. Jin, PRL 98, (2007)

16. A way to “see” molecules
Create molecules
V(R) R
about 60 +/- 30 mG difference in x intercept, 11% difference in slope N=140,000, EF=8.2 kHz
Look for energetic atoms created by tunneling

17. A way to “see” moleculesB
about 60 +/- 30 mG difference in x intercept, 11% difference in slope N=140,000, EF=8.2 kHz
ml = ±1
ml = 0

18. A way to “see” moleculesB
about 60 +/- 30 mG difference in x intercept, 11% difference in slope N=140,000, EF=8.2 kHz
ml = ±1
ml = 0

19. Molecule lifetime B time ml = ±1 t =1.2 ms molecule creation resonance
hold time
ml = ±1
about 60 +/- 30 mG difference in x intercept, 11% difference in slope N=140,000, EF=8.2 kHz
t =1.2 ms

20. Quasi-bound molecule lifetime
molecule creation B
resonance
time
hold time

21. Molecule Lifetimes ml = 0 ml = ±1
J.P. Gaebler, J.T. Stewart, J.L. Bohn, & D.S. Jin, PRL 98, (2007)

22. Dipolar relaxation
Since our atoms are not in the lowest energy spin state,
the molecules can undergo “one-body” decay.
bound free
This decay process would not exist for atoms in the lowest energy spin state (6Li has such a p-wave resonance).

23. Collisional decay t = 7 ± 1 ms ml = 0
After removing atoms (blasting with resonant light)
t = 7 ± 1 ms
ml = 0

24. What’s next?
ml = 0
ml = ±1

25. Molecule Creation B time ml = ±1 ml = 0 resonance
about 60 +/- 30 mG difference in x intercept, 11% difference in slope N=140,000, EF=8.2 kHz

26. Molecule Creation

27. Molecule Creation

28. Conclusion:
We can create and detect p-wave Feshbach molecules in a Fermi gas of atoms.
Novel aspects include:
Centrifugal barrier
Quasi-bound state
Narrow resonance
The molecule lifetime is short.
V(R) R

29. P-wave molecule work: Jayson Stewart, John Gaebler
Group Members
J. Goldwin
P-wave molecule work: Jayson Stewart, John Gaebler M.
Olsen