Pinpointing Feshbach resonances and testing Efimov universalities in 39K

Using a combination of bound-state spectroscopy and loss spectroscopy, we pinpoint eight intrastate Feshbach resonances in 39K, as well as six previously unexplored interstate ones. We perform a detailed characterization of four of the intrastate resonances and two of the interstate ones. We carry out coupled-channel scattering calculations and find good agreement with experiment. The combination of experiment and theory provides a faithful map of the scattering length a and permits precision measurements of the signatures of Efimov physics across four intermediate-strength intrastate resonances. We measure the modulation of the a4 scaling of the three-body loss coefficient for both a < 0 and a > 0, as well as the many-body loss dynamics at unitarity (where a diverges). The absolute positions of the observed Efimov features confirm a ubiquitous breakdown of Efimov- van der Waals universality in 39K, while their relative positions are in agreement with the universal Efimov ratios. The loss dynamics at unitarity are the same (within experimental uncertainties) for the three broadest Feshbach resonances, consistent with observing little variation in the widths of the corresponding Efimov features.

Automated summary

By combining bound-state spectroscopy and loss spectroscopy, we identified eight intrastate and six interstate Feshbach resonances in 39K. We characterized four intrastate and two interstate resonances, and our coupled-channel scattering calculations matched well with the experimental results. This study provides a precise map of the scattering length and allows for precise measurements of Efimov physics phenomena.