Asymmetric Lineshapes of Efimov Resonances in Mass-Imbalanced Ultracold Gases

Abstract

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 lineshape that originates from the coexistence of Efimov resonances with Stückelberg interference minima. These asymmetric lineshapes are quantified utilizing the Fano profile formula. 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|→∞, 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.

Efimov resonance position near a narrow Feshbach resonance in $^6$Li-$^{133}$Cs mixture

“…The few-body aspects of heteronuclear mixtures attracted significant interest in the last decade, both theoretical [11][12][13][14][15][16][17][18][19][20][21] and experimental [22][23][24][25][26][27][28][29]. The 6 Li-133 Cs mixture is the most extreme mass imbalanced system in which Efimov features were observed up to date making it favorable for the attempt to reveal the few-body physics at a narrow Feshbach resonance.…”

Dynamical excitation processes and correlations of three-body two-dimensional mixtures

“…Apart from the particle statistics, our study addresses the effect of unequal massed three-body collisions. In 3D gases, it is known that highly mass-imbalanced systems exhibit rich resonant effects [46][47][48][49][50][51], or they favor the observation of multiple successive Efimov states [52][53][54]. Therefore, the inclusion of unequal masses here provides a comprehensive description of the dynamic properties of 2D threebody collisions ranging from light-light-heavy (LLH) to heavy-heavy-light (HHL) systems.…”