  We explore the convergence of the light-front coupled-cluster (LFCC) method
in the context of two-dimensional quenched scalar Yukawa theory. This theory is
simple enough for higher-order LFCC calculations to be relatively
straightforward. The quenching is to maintain stability; the spectrum of the
full theory with pair creation and annihilation is unbounded from below. The
basic interaction in the quenched theory is only emission and absorption of a
neutral scalar by the complex scalar. The LFCC method builds the eigenstate
with one complex scalar and a cloud of neutrals from a valence state that is
just the complex scalar and the action of an exponentiated operator that
creates neutrals. The lowest order LFCC operator creates one; we add the next
order, a term that creates two. At this order there is a direct contribution to
the wave function for two neutrals and one complex scalar and additional
contributions to all higher Fock wave functions from the exponentiation.
Results for the lowest order and this new second-order approximation are
compared with those obtained with standard Fock-state expansions. The LFCC
approach is found to allow representation of the eigenstate with far fewer
functions than the number of wave functions required in a converged Fock-state
expansion.
