  We consider a Bose-Josephson junction (BJJ) formed by a binary mixture of
ultracold atoms to investigate the manifestation of coherent collective
dynamics on ergodicity and quantum scars, unfolding the connection between
them. By tuning the inter- and intra-species interaction, we demonstrate a rich
variety of Josephson dynamics and transitions between them, which plays a
crucial role in controlling the overall ergodic behavior. The signature of
underlying classicality is revealed from the entanglement spectrum, which also
elucidates the formation of quantum scars of unstable steady states and of
periodic orbits leading to athermal behavior. The degree of ergodicity across
the energy band and scarring phenomena can be probed from the auto-correlation
function as well from the phase fluctuation of the condensates, which has
relevance in cold atom experiments.
