  We study the correlation length of the two-dimensional Edwards-Anderson Ising
spin glass with bimodal interactions using a combination of parallel tempering
Monte Carlo and a rejection-free cluster algorithm in order to speed up
equilibration. Our results show that the correlation length grows ~ exp(2J/T)
suggesting through hyperscaling that the degenerate ground state is separated
from the first excited state by an energy gap ~4J, as would naively be
expected.
