Dynamics of equilibration and collisions in ultradilute quantum droplets

Abstract

Employing time-dependent density-functional theory, we have studied dynamical equilibration and binary head-on collisions of quantum droplets made of a ${}^{39}$K-${}^{39}$K Bose mixture. The phase space of collision outcomes is extensively explored by performing fully three-dimensional calculations with effective single-component QMC based and two-components LHY-corrected mean-field functionals. We exhaustively explored the important effect -- not considered in previous studies -- of the initial population ratio deviating from the optimal mean-field value $N_2/N_1=\sqrt{a_{11}/a_{22}}$. Both stationary and dynamical calculations with an initial non-optimal concentration ratio display good agreement with experiments. Calculations including three-body losses acting only on the $|F,m_F⟩=|1,0⟩$ state show dramatic differences with those obtained with the three-body term acting on the total density.