  A nonlinear screening theory is formulated to study the problem of gap
formation and its relation to glassy freezing in classical Coulomb glasses. We
find that a pseudo-gap ("plasma dip") in a single-particle density of states
begins to open already at temperatures comparable to the Coulomb energy. This
phenomenon is shown to reflect the emergence of short range correlations in a
liquid (plasma) phase, a process which occurs even in the absence of disorder.
Glassy ordering emerges when disorder is present, but this occurs only at
temperatures more then an order of magnitude lower, which is shown to follow
from nonlinear screening of the Coulomb interaction. Our result suggest that
the formation of the "plasma dip" at high temperatures is a process distinct
from the formation of the Efros-Shklovskii (ES) pseudo-gap, which in our model
emerges only within the glassy phase.
