Transport of a Single Cold Ion Immersed in a Bose-Einstein Condensate

We investigate transport dynamics of a single low-energy ionic impurity in Bose-Einstein condensate. The is implanted into the condensate starting from Rydberg excitation, which ionized by sequence fast electric field pulses aiming to minimize ion's initial kinetic energy. Using small bias field, we study subsequent collisional subject an external force. ion-atom collision rate, stemming dense degenerate host gas and large scattering cross section, allows us regime frequent collisions within only tens microseconds. Comparison our measurements with stochastic trajectory simulations based on sequential Langevin indicate diffusive properties measure its mobility. Furthermore, working free untrapped ion provides unique means distinguish realizations, where inelastic molecular-ion formation via three-body recombination. cold chemistry these events find evidence for rovibrational quenching produced molecule. Our results open novel path charged quantum impurities ultracold matter.