  Combining two Bose-Einstein condensates (BECs) may result in a miscible or
immiscible mixture, or even a violent implosion. We theoretically demonstrate
that dipolar two-component BECs produce far richer physics than their
nondipolar counterparts. Intriguingly, when both components have equivalent
dipoles, the transition to immiscibility is largely unaffected by dipolar
physics, yet the dipoles maximally affect stability. Conversely, antiparallel
dipoles strongly affect miscibility but have little effect on stability. By
performing three-dimensional calculations of the ground states and their
excitations, we find strong dependencies on the confinement geometry. We
explore and elucidate the various phononic and rotonic phase transitions, as
well as symmetry preserving crossovers.
