  We investigate the finite-temperature screening behavior of three-dimensional
U(1) spin liquid phases with fracton excitations. Several features are shared
with the conventional U(1) spin liquid. The system can exhibit spin liquid
physics over macroscopic length scales at low temperatures, but screening
effects eventually lead to a smooth finite-temperature crossover to a trivial
phase at sufficiently large distances. However, unlike more conventional U(1)
spin liquids, we find that complete low-temperature screening of fractons
requires not only very large distances, but also very long timescales. At the
longest timescales, a charged disturbance (fracton) will acquire a screening
cloud of other fractons, resulting in only short-range correlations in the
system. At intermediate timescales, on the other hand, a fracton can only be
partially screened by a cloud of mobile excitations, leaving weak power-law
correlations in the system. Such residual power-law correlations may be a
useful diagnostic in an experimental search for U(1) fracton phases.
