  We report experimental evidence of a Gardner-like transition from variable to
persistent force contacts in a two-dimensional, bidisperse granular crystal by
analyzing the variability of both particle positions and force networks formed
under uniaxial compression. Starting from densities just above the freezing
transition, and for variable amounts of additional compression, we compare
configurations to both their own initial state, and to an ensemble of
equivalent, reinitialized states. This protocol shows that force contacts are
largely undetermined when the density is below a Gardner-like transition, after
which they gradually transition to being persistent, being fully so only above
the jamming point. We associate the disorder that underlies this effect to the
size of the microscopic asperities of the photoelastic disks used, by analogy
to other mechanisms that have been previously predicted theoretically.
