  We demonstrate the role of interactions in driving the relaxation of an
isolated integrable quantum system following a sudden quench. We consider a
family of integrable hard-core lattice anyon models that continuously
interpolates between noninteracting spinless fermions and strongly interacting
hard-core bosons. A generalized Jordan-Wigner transformation maps the entire
family to noninteracting fermions. We find that, aside from the singular
free-fermion limit, the entire single-particle density matrix and therefore all
one-body observables relax to the predictions of the generalized Gibbs ensemble
(GGE). This demonstrates that, in the presence of interactions, correlations
between particles in the many-body wave function provide the effective
dissipation required to drive relaxation of all one-body observables to the
GGE. This relaxation does not depend on translational invariance, or the
tracing out of any spatial domain of the system.
