Feshbach resonances in the 6Li-40K Fermi-Fermi mixture: elastic versus inelastic interactions

Abstract

We present a detailed theoretical and experimental study of Feshbach resonances in the 6 Li-40 K mixture. Particular attention is given to the inelastic scattering properties, which have not been considered before. As an important example, we thoroughly investigate both elastic and inelastic scattering properties of a resonance that occurs near 155 G. Our theoretical predictions based on a coupled channels calculation are found in excellent agreement with the experimental results. We also present theoretical results on the molecular state that underlies the 155 G resonance, in particular concerning its lifetime against spontaneous dissociation. We then present a survey of resonances in the system, fully characterizing the corresponding elastic and inelastic scattering properties. This provides the essential information to identify optimum resonances for applications relying on interaction control in this Fermi-Fermi mixture.

Metastability and coherence of repulsive polarons in a strongly interacting Fermi mixture

“…This process was identified in Ref. [21] as a source of losses. However, this relaxation is about an order of magnitude slower than the measured decay rate of the repulsive polaron and thus does not affect our measurements.…”

“…In a particular combination of spin states [21], the 6 Li - 40 K mixture features a Feshbach resonance centered at B 0 = 154.719(2) G. The resonance allows to widely tune the s-wave interaction, parametrised by the scattering length a, via a magnetic field B. The interaction strength is described by the dimensionless parameter −1/(κ F a), where κ F =h −1 √ 2m Li ε F = 1/(2850 a 0 ) is the Fermi wave number; hereh = h/2π, a 0 is Bohr's radius, and m Li is the mass of a 6 Li atom.…”

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

“…Although the superfluid phase transition of this Fermi-Fermi mixture has not been reported yet, the Fermi degenerate regime has been achieved [20,24]. In addition, since a tunable interaction associated with a Feshbach resonance between 6 Li and 40 K atoms [19,22,23], as well as the formation of 6 Li-40 K hetero molecules [21], has been realized, the observation of superfluid behaviors seems imminent.…”

Hydrodynamic Expansion of a Strongly Interacting Fermi-Fermi Mixture

“…The introduction of population imbalance [6,7] then paved the way to the rich physics of polarized Fermi gases [8,9]. The recent experimental efforts to create ultracold mixtures of two different fermionic species [10][11][12][13][14][15][16][17] have brought the field close to a new research frontier with intriguing new possibilities, e.g. related to novel types of superfluids and quantum phases [18,19] and to new few-body states [20,21].…”

“…Interaction control is achieved by the 155 G interspecies Feshbach resonance, which occurs for Li in its lowest internal state (m Li f = +1/2) and K in its third to lowest state (m K f = −5/2) [11,12,17]. The s-wave scattering length a can be tuned according to the standard resonance expression a = a bg (1 − ∆/(B − B 0 )) with a bg = 63.0 a 0 (a 0 is Bohr's radius), ∆ = 880 mG, and B 0 = 154.707(5) G [17].…”