Universality of weakly bound dimers and Efimov trimers close to Li-Cs Feshbach resonances

TL;DR

This study investigates the scattering properties of ultracold Li-Cs mixtures near Feshbach resonances, creating weakly bound dimers, refining resonance parameters, and exploring implications for Efimov physics and universal trimer scaling.

Contribution

The paper provides precise measurements of Li-Cs Feshbach resonances and constructs accurate molecular potentials, advancing understanding of Efimov states and universal trimer behavior.

Findings

Improved precision in resonance pole positions and widths.

Observation of weakly bound LiCs dimers near Feshbach resonances.

Discussion of Efimov scenario and universal trimer scaling.

Abstract

We study the interspecies scattering properties of ultracold Li-Cs mixtures in their two energetically lowest spin channels in the magnetic field range between 800 G and 1000 G. Close to two broad Feshbach resonances we create weakly bound LiCs dimers by radio-frequency association and measure the dependence of the binding energy on the external magnetic field strength. Based on the binding energies and complementary atom loss spectroscopy of three other Li-Cs s-wave Feshbach resonances we construct precise molecular singlet and triplet electronic ground state potentials using a coupled-channels calculation. We extract the Li-Cs interspecies scattering length as a function of the external field and obtain almost a ten-fold improvement in the precision of the values for the pole positions and widths of the s-wave Li-Cs Feshbach resonances as compared to our previous work [Pires \textit{et al.}, Phys. Rev. Lett. \textbf{112}, 250404 (2014)]. We discuss implications on the Efimov scenario and the universal geometric scaling for LiCsCs trimers.