  The existence of an equilibrium glassy phase for charges in a disordered
potential with long-range electrostatic interactions has remained controversial
for many years. Here we conduct an extensive numerical study of the
disorder-temperature phase diagram of the three-dimensional Coulomb glass model
using population annealing Monte Carlo to thermalize the system down to
extremely low temperatures. Our results strongly suggest that, in addition to a
charge order phase, a transition to a glassy phase can be observed, consistent
with previous analytical and experimental studies.
