Collapse of Bose component in Bose-Fermi mixture with attraction between components

An effective Hamiltonian for the Bose system in the mixture of ultracold atomic clouds of bosons and fermions is obtained by integrating out the Fermi degrees of freedom. An instability of the Bose system is found in the case of attractive interaction between components in good agreement with the experiment on the bosonic $^{87}$Rb and fermionic $^{40}$K mixture.