  We investigate charge transport within some background medium by means of an
effective lattice model with a novel form of fermion-boson coupling. The bosons
describe fluctuations of a correlated background. By analyzing groundstate and
spectral properties of this transport model, we show how a metal-insulator
quantum phase transition can occur for the half-filled band case. We discuss
the evolution of a mass-asymmetric band structure in the insulating phase and
establish connections to the Mott and Peierls transition scenarios.
