Bright solitons in Bose-Fermi mixtures

TL;DR

This paper investigates the conditions under which bright solitons can form in a Bose-Fermi mixture confined in a three-dimensional elongated trap, highlighting the role of interspecies attraction and stability criteria.

Contribution

It demonstrates that strong Bose-Fermi attraction can induce bright solitons in the mixture without collapse, even at natural scattering lengths.

Findings

Bright solitons can form in Bose-Fermi mixtures with sufficient interspecies attraction.

Stable soliton structures are possible without collapse under certain conditions.

Formation of solitons is feasible at natural scattering lengths in elongated traps.

Abstract

We consider the formation of bright solitons in a mixture of Bose and Fermi degenerate gases confined in a three-dimensional elongated harmonic trap. The Bose and Fermi atoms are assumed to effectively attract each other whereas bosonic atoms repel each other. Strong enough attraction between bosonic and fermionic components can change the character of the interaction within the bosonic cloud from repulsive to attractive making thus possible the generation of bright solitons in the mixture. On the other hand, such structures might be in danger due to the collapse phenomenon existing in attractive gases. We show, however, that under some conditions (defined by the strength of the Bose-Fermi components attraction) the structures which neither spread nor collapse can be generated. For elongated enough traps the formation of solitons is possible even at the ``natural'' value of the mutual Bose-Fermi ($^{87}$Rb -$^{40}$K in our case) scattering length.