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 N2/N1 = a11/a22. 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, mF = |1, 0 state show dramatic differences with those obtained with the three-body term acting on the total density.

Merging of superfluid Helium nanodroplets with vortices

“…[7][8][9][10] What makes protrusions unique in the case of 4 He droplets is that they act as nucleation sites of quantized vortex rings. Surface protrusions have also been identified in head-on collisions of self-bound quantum droplets, 13,34 but no vortex ring nucleation has been reported in these studies. For these droplets made of ultradilute Bose-gase mixtures, a minimum number of atoms is needed to develop any binding, and the surface tension is very small.…”

“…25,26 With the experimental realization of stable self-bound ultradilute "quantum droplets" made of bosonic atoms of a binary mixture, 70 which have been found to sustain quantum vortices, 71 it has been possible to study the collision of self-bound BECs. 13,34 Thus, it should also be possible to study the merging of quantum droplets and the influence of surface effects in the transfer of angular momentum from one quantum droplet to another, as well as a deeper analysis of the role of the surface protrusions as potential nucleation sites of vortex rings, thus connecting the ultradilute quantum droplet BECs and the superfluid 4 He droplets scenarios.…”

Dilute quantum liquid in a K-Rb Bose mixture

“…Recently, collisions between two droplets have been proposed as a useful experimental tool to investigate the dynamical properties of self-bound systems [12]. When two such droplets approach each other with a given relative velocity, they can either merge in a single droplet (coalescence) or separate into two or more droplets after the collision (bouncing/fragmentation) [13]. These different outcomes depend on whether or not the surface tension is large enough to counterbalance the kinetic energy of the colliding drops.…”