Quantum droplet of one-dimensional bosons with a three-body attraction

Ultracold atoms offer valuable opportunities where interparticle interactions can be controlled at will. In particular, by extinguishing the two-body interaction, one can realize unique systems governed by the three-body interaction, which is otherwise hidden behind the two-body interaction. Here we study one-dimensional bosons with a weak three-body attraction and show that they form few-body bound states as well as a many-body droplet stabilized by the quantum mechanical effect. Their binding energies relative to that of three bosons are all universal and the ground-state energy of the dilute droplet is found to grow exponentially as E_N/E₃→exp(8 N²/√{3 }π ) with increasing particle number N ≫1 . The realization of our system with coupled two-component bosons in an optical lattice is also discussed.