In the first part of the talk I will discuss the problem of generating three-body and higher-order interactions in an ultracold gas. A mechanism is proposed which can be implemented for dipolar bosons in the bilayer configuration with tunneling or in an atomic system by using radio-frequency fields to couple two hyperfine states [1,2]. In the second part I will talk about a three-dimensional condensed Bose-Bose mixture in the regime where the interspecies attraction is stronger than the geometrical average of the intraspecies repulsions. From the mean-field viewpoint such a mixture should collapse but beyond mean-field effects stabilize it. Instead of collapsing, the gas gets into a droplet state, physical properties of which I will discuss [3]. A similar stabilization mechanism has recently been observed experimentally in Bose-condensed droplets of magnetic dipoles in Stuttgart [4].

References

[1] D. S. Petrov, Phys. Rev. Lett. 112, 103201 (2014)

[2] D. S. Petrov, Phys. Rev. A 90, 021601(R) (2014)

[3] D. S. Petrov, Phys. Rev. Lett. 115, 155302 (2015)

[4] I. Ferrier-Barbut, H. Kadau, M. Schmitt, M. Wenzel, and T. Pfau, arXiv:1601.03318 (2016)