Interplay between timescales governs residual activity in harmonically bound active Brownian dynamics

Microswimmers, both natural and artificial, when in an external force field, show rich dynamical features, such as anomalous diffusion, self-organized collective phases, and ergodicity breaking due to the interplay between the potential and self-propulsion of the active particle. Here, we studied the phoretically active self-driven Pt-coated silica Janus colloid in an optical trap and modeled the system as a harmonically bound active Brownian particle for numerical simulations of the Langevin's equation. Our results show a novel dynamical crossover from active propulsion dominated Boltzmann-like bound trajectories to annularly confined trajectories exhibiting non-ergodic behavior. This transition is governed by the ratio between two characteristic timescales: persistence time of the active propulsion and equilibration time in harmonic confinement, and with no effect of the propulsion speed of the particle. We expect our results to be relevant for optical and thermal micromanipulation of various self-driven active particles in complex environments, their applications in remote sensing, autonomous microrobots, etc.