Bose-Fermi Mixtures in a Three-dimensional Optical Lattice

TL;DR

This study investigates how Bose-Fermi mixtures in a 3D optical lattice affect phase coherence, density, and cooling, revealing that fermions reduce bosonic coherence and can facilitate sympathetic cooling.

Contribution

It provides experimental insights into the effects of fermionic admixture on bosonic coherence and density, and suggests a mechanism for sympathetic cooling in optical lattices.

Findings

Fermionic admixture diminishes bosonic phase coherence.

Attractive interactions increase boson density in the lattice.

No three-body loss observed for fermionic atoms.

Abstract

We have studied mixtures of fermionic $^{40}$K and bosonic $^{87}$Rb quantum gases in a three-dimensional optical lattice. We observe that an increasing admixture of the fermionic species diminishes the phase coherence of the bosonic atoms as measured by studying both the visibility of the matter wave interference pattern and the coherence length of the bosons. Moreover, we find that the attractive interactions between bosons and fermions lead to an increase of the boson density in the lattice which we measure by studying three-body recombination in the lattice. In our data we do not observe three-body loss of the fermionic atoms. An analysis of the thermodynamics of a noninteracting Bose-Fermi mixture in the lattice suggests a mechanism for sympathetic cooling of the fermions in the lattice.