Three-Body Recombination in a Three-State Fermi Gas with Widely Tunable Interactions

Abstract

We investigate the stability of a three spin state mixture of ultracold fermionic 6 Li atoms over a range of magnetic fields encompassing three Feshbach resonances. For most field values, we attribute decay of the atomic population to three-body processes involving one atom from each spin state and find that the three-body loss coefficient varies by over four orders of magnitude. We observe high stability when at least two of the three scattering lengths are small, rapid loss near the Feshbach resonances, and two unexpected resonant loss features. At our highest fields, where all pairwise scattering lengths are approaching at = −2140a0, we measure a three-body loss coefficient L3 ≃ 5 × 10 −22 cm 6 /s and a trend toward lower decay rates for higher fields indicating that future studies of color superfluidity and trion formation in a SU(3) symmetric Fermi gas may be feasible.

Three-body parameter for Efimov states inLi6

“…The scattering length has a pole at resonance, corresponding to a two-body bound state exactly at threshold. Signatures of Efimov states were first observed in an ultracold gas of cesium atoms [7] and have since been found in many other systems, including other bosonic gases [8][9][10][11][12][13], three-component fermionic spin mixtures [14][15][16][17], and mixtures of atomic species [18][19][20][21]. Moreover, extensions of the Efimov scenario to universal states of larger clusters [22][23][24] have been demonstrated in experiments [9,25,26], highlighting the general nature of universal few-body physics.…”

“…After a spatial integration of losses over the density profile of the trapped cloud, the loss rate coefficient L 3 can be experimentally determined by fitting the time-dependent decay of the total atom numbers [14][15][16]. Efimov states show up as distinct loss resonances [36] when they couple to the three-atom threshold.…”

Thermodynamics of Ultracold Fermi Gases

“…By using a di erent fermionic species, or using a recent proposal for tuning the potential range using an electric eld [253], we could simulate neutron matter in the crust of neutron stars up to larger densities [60]. Simulating quantum chromodynamics models, such as color superconductivity models, could also be investigated using Bose-Fermi mixtures [61] or three-component Fermi gases [254,255], the realization of the latter being the subject or current active research [256,257]. Finally, problems of quantum magnetism [258,14] could be addressed using ultracold atoms in optical lattices.…”

Dynamical instability of a spin spiral in an interacting Fermi gas as a probe of the Stoner transition

“…Interestingly we observe that the ratio of loss to growth rate depends only on the interaction strength and not on the spiral pitch Q. Comparing the two rates we find that the loss will dominate for strong interactions k F a 4.9, though in this regime the formula for loss rate significantly overestimates the true loss [17] and in fact the theory should be valid for even higher interaction strengths. However, in the experimentally accessible region including the phase transition, k F a < 2.5, loss is more than 60 times smaller than the dominant growth rate of the collective modes.…”