Three-body force and beyond in low-dimensional ultracold atoms

I will give a brief and partial overview of three-body force and beyond in low-dimensional ultracold atoms.

Three-body and higher-body forces naturally appear in physics of ultracold atoms when atoms are confined into low dimensions. Although they are quantitatively weak compared to a two-body force, the three-body force in one dimension turns out to be the leading perturbation to break the integrability. Therefore, it is capable of causing qualitatively significant consequences regarding thermalization, thermal trasnport, and cluster formation of bosons in quasi-one-dimension.

Three-body and higher-body forces can also be controlled artificially with ultracold atoms. A simple and versatile scheme allows us to realize exotic systems without two-body but with tunable three-body forces and even more exotic systems without two- body and three-body but with four-body forces in any dimensions. Such exotic systems are predicted to exhibit unique physics such as semisuper Efimov effect for two-dimensional bosons, quantum droplet formation, and five-body Efimov effect for one-dimensional bosons.