An atomic Fermi gas near a p-wave Feshbach resonance D. Jin JILA, NIST and the University of Colorado Replace image with new group photo $ NSF, NIST

Outline Motivation A p-wave Feshbach resonance Molecule energies and lifetimes Future Replace image with photo

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

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

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)

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)

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

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

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

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, 053201 (2003)

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, 042712 (2004).

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

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, 070403 (2005) association S.T. Thompson, E. Hodby, & C.E. Wieman, PRL 94, 190404 (2005) V(R) R centrifugal barrier B below both resonances 162 mG below m=1 resonance

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

P-wave molecule energy B ml = ±1 ml = 0 190 kHz/G J.P. Gaebler, J.T. Stewart, J.L. Bohn, & D.S. Jin, PRL 98, 200403 (2007)

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

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

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

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

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

Molecule Lifetimes ml = 0 ml = ±1 J.P. Gaebler, J.T. Stewart, J.L. Bohn, & D.S. Jin, PRL 98, 200403 (2007)

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).

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

What’s next? ml = 0 ml = ±1

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

Molecule Creation

Molecule Creation

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

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