  We study the relaxation dynamics of strongly interacting quantum systems that
display a kind of many-body localization in spite of their
translation-invariant Hamiltonian. We show that dynamics starting from a random
initial configuration is nonperturbatively slow in the hopping strength, and
potentially genuinely nonergodic in the thermodynamic limit. In finite systems
with periodic boundary conditions, density relaxation takes place in two
stages, which are separated by a long out-of-equilibrium plateau whose duration
diverges exponentially with the system size. We estimate the phase boundary of
this quantum glass phase, and discuss the role of local resonant
configurations. We suggest experimental realizations and methods to observe the
discussed nonergodic dynamics.
