Interaction-driven Dynamics of 40K / 87Rb Fermi-Bose Gas Mixtures in the Large Particle Number Limit

TL;DR

This study investigates the effects of interspecies attraction in a large particle number Fermi-Bose mixture of 40K and 87Rb, observing mean field-driven collapse, revivals, and altered expansion profiles, with detailed decay dynamics and loss coefficients.

Contribution

It provides the first detailed experimental analysis of collapse and revival phenomena in large particle number Fermi-Bose mixtures, including precise measurements of three-body loss coefficients.

Findings

Observed mean field-driven collapse at critical particle numbers.

Detected revivals of collapse beyond critical numbers.

Measured the three-body loss coefficient K3 for the mixture.

Abstract

We have studied effects of interspecies attraction in a Fermi-Bose mixture over a large regime of particle numbers in the 40K / 87Rb system. We report on the observation of a mean field driven collapse at critical particle numbers of 1.2 million 87Rb atoms in the condensate and 750,000 40K atoms consistent with mean field theory for an interspecies scattering length of -281(15) Bohr radii [S. Inouye et al., Phys. Rev. Lett. 93, 183201 (2004)]. For overcritical particle numbers, we see evidence for revivals of the collapse. Before and after the collapse, the axial expansion profileof the 40K cloud is strongly modified and reflects the in-trap density profile distorted by the mean field interspecies attraction. Part of our detailed study of the decay dynamics and mechanisms is a measurement of the (87Rb - 87Rb- 40K) three-body loss coefficient K3=(2.8+-1.1)*10^-28 cm^6/s, which is an important input parameter for dynamical studies of the system.