A distinguishing feature of ultracold collisions of bosonic lithium atoms is the presence of two near-degenerate two-body continua. The influence of such a near degeneracy on the few-body physics in the vicinity of a narrow Feshbach resonance is investigated within the framework of a minimal model with two atomic continua and one closed molecular channel. The model allows analysis of the spin composition of loosely bound dimers and trimers. In the two-body sector the well-established coupled-channel calculation phenomenology of lithium is qualitatively reproduced, and its particularities are emphasized and clarified. In the three-body sector we find that the Efimov trimer energy levels follow a different functional form as compared to a single continuum scenario while the thresholds remain untouched. This three-channel model with two atomic continua complements our earlier developed three-channel model with two molecular channels [Yudkin and Khaykovich, Phys. Rev. A 103, 063303 (2021)] and suggests that the experimentally observed exotic behavior of the first excited Efimov energy level (Yudkin, Elbaz, and Khaykovich, arXiv:2004.02723) is most probably caused by the short-range details of the interaction potential.A distinguishing feature of ultracold collisions of bosonic lithium atoms is the presence of two near-degenerate two-body continua. The influence of such a near degeneracy on the few-body physics in the vicinity of a narrow Feshbach resonance is investigated within the framework of a minimal model with two atomic continua and one closed molecular channel. The model allows analysis of the spin composition of loosely bound dimers and trimers. In the two-body sector the well-established coupled-channel calculation phenomenology of lithium is qualitatively reproduced, and its particularities are emphasized and clarified. In the three-body sector we find that the Efimov trimer energy levels follow a different functional form as compared to a single continuum scenario while the thresholds remain untouched. This three-channel model with two atomic continua complements our earlier developed three-channel model with two molecular channels [Yudkin and Khaykovich, Phys. Rev. A 103, 063303 (2021)] and suggests that the experimentally observed exotic behavior of the first excited Efimov energy level (Yudkin, Elbaz, and Khaykovich, arXiv:2004.02723) is most probably caused by the short-range details of the interaction potential.

arXiv:2301.08097Physical Review AMay 2, 20235 citations

Universality in Three and Four-Body Efimov States

Randall G. Hulet

APSApr 1, 20110 citations

Fano profiles of Efimov resonances in mass-imbalanced ultracold gases

Panagiotis Giannakeas, Chris H. Greene

The resonant profile of the rate coefficient for three-body recombination into a shallow dimer is investigated for mass-imbalanced systems. In the low-energy limit, three atoms collide with zero-range interactions, in a regime where the scattering lengths of the heavy-heavy and the heavy-light subsystems are positive and negative, respectively. For this physical system, the adiabatic hyperspherical representation is combined with a fully semi-classical method and we show that the shallow dimer recombination spectra display an asymmetric Fano lineshape that originates from the coexistence of Efimov resonances with Stuckelberg interference minima. In particular, a closed form expression is derived that describes the width of the corresponding Efimov resonances and the Fano lineshape asymmetry parameter $q$ . The profile of Efimov resonances exhibits a $q-$ reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e. $|q|\to \infty$ , we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom-dimer continua, and the corresponding Efimov metastable states behave as bound levels.The resonant profile of the rate coefficient for three-body recombination into a shallow dimer is investigated for mass-imbalanced systems. In the low-energy limit, three atoms collide with zero-range interactions, in a regime where the scattering lengths of the heavy-heavy and the heavy-light subsystems are positive and negative, respectively. For this physical system, the adiabatic hyperspherical representation is combined with a fully semi-classical method and we show that the shallow dimer recombination spectra display an asymmetric Fano lineshape that originates from the coexistence of Efimov resonances with Stuckelberg interference minima. In particular, a closed form expression is derived that describes the width of the corresponding Efimov resonances and the Fano lineshape asymmetry parameter $q$. The profile of Efimov resonances exhibits a $q-$reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e. $|q|\to \infty$, we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom-dimer continua, and the corresponding Efimov metastable states behave as bound levels.

Sep 28, 20210 citations

q

. The profile of Efimov resonances exhibits a

q-

reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e.

|q|\to \infty

, we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom-dimer continua, and the corresponding Efimov metastable states behave as bound levels.