Formation of fermionic molecules via interisotope Feshbach resonances

Abstract

We perform an analysis of recent experimental measurements and improve the lithium interaction potentials. For 6 Li a consistent description can be given. We discuss theoretical uncertainties for the position of the wide 6 Li Feshbach resonance, and we present an analytic scattering model for this resonance, based on the inclusion of a field-dependent virtual open-channel state. We predict new Feshbach resonances for the 6 Li-7 Li system, and their importance for different types of crossover superfluidity models is discussed.

Study of Efimov physics in two nuclear-spin sublevels of 7Li

“…In Fig. 2 we show the dipolar relaxation rate coefficients as a function of magnetic field which were calculated via a coupledchannels calculation by using recent interaction potentials [18]. Except for two peaks which signify Feshbach resonances, the loss rate coefficients are extremely small, ∼ 3 orders of magnitude smaller than the corresponding measured rate coefficients, if the experimental losses were treated as purely two-body related.…”

“…In order to make a correct mapping between binding energy and scattering length, we make use of a coupled-channels two-body interaction model for lithium, which has been discussed earlier [18], and we use the interaction potentials discussed there as a starting point for our analysis. For large interatomic separations r the singlet (S = 0) and a triplet (S = 1) potentials are given by…”

Strongly interacting isotopic Bose-Fermi mixture immersed in a Fermi sea

“…These systems are plagued by typically unequal trapping potentials and the large mass difference between unlike atoms, causing gravitational sag that has to be compensated. Predictions for Feshbach resonances in isotopic Bose-Fermi mixtures are available for 3 He-4 He [32] and for 6 Li-7 Li [33], with preliminary experimental findings reported in [34]. An atom-molecule mixture of 6 Li-6 Li 2 allowed access to a part of the phase diagram of strongly interacting bosons and fermions [35].…”

Ultracold Fermionic Feshbach Molecules ofNa23K40

“…Since the background scattering length a bg = −690 +90 −130 is large and negative [13][25], the closed channel molecular state is predominantly coupled to a virtual state [26,27] of energy E vs = 2 2µ(a bg −ā) = k B ×11(3) µK. In this case, the binding energy E b is given by solving…”

“…Here, E c (B) is the magnetic field dependent energy of the closed channel molecule relative to the scattering threshold, known from the asymptotic bound state model [13], and A vs is the squared magnitude of the coupling matrix element between the closed channel molecular state and the virtual state [26,27]. With A vs as the only fit parameter, we obtain excellent agreement with the data, finding A vs = (h × 5.2(6) MHz) 2 .…”