Three-body Physics in the Impurity Limit of 39K Bose-Einstein Condensates

Abstract

Loss spectroscopy is a key tool for investigating systems where important system parameters are linked to intrinsic resonant loss processes. We investigate loss processes of impurity atoms embedded in a medium of a Bose-Einstein Condensate close to a Feshbach resonance. In this case, three-body loss processes occur faster than the measurement duration, impeding a direct time-resolved measurement. Here, we discuss how an even faster two-body loss process can be used to probe the system. The time-dependent number of atoms in the medium is reconstructed from such measurements, allowing for the extraction of the three-body loss rate coefficient $L_3$ and its scaling with scattering length. Moreover, the medium atom number is reconstructed from spectroscopic loss measurements. This allows for a comparison of the medium densities based on both the extracted loss rates and the spectroscopically reconstructed atom number. Finally, the number of lost medium atoms per loss event is evaluated and found to exceed 2 at strong interactions, which is attributed to secondary collisions in the medium. These investigations establish the use of a fast loss mechanism as a new tool in the field and provide quantitative measurements of three-body losses at large interaction strengths.