Quantum Transport within a Background Medium: Fluctuations versus Correlations

We investigate transport within some background medium by means of an effective lattice model with a novel form of fermion-boson coupling. The bosons correspond to local fluctuations of the background. The model captures the principal transport mechanisms that apply to a great variety of physical systems. and can be applied, e.g. in the one-particle sector, to describe the motion of lattice and spin polarons, or the dynamics of a particle coupled to a bath. Performing large-scale numerical simulations on the HLRB-II at LRZ Munich, based on highly efficient variational Lanczos and Chebyshev moment expansion techniques, we analyse the newly proposed model by exactly calculating the single quasiparticle effective mass, ground-state dispersion and spectral function, as well as the Drude weight and the optical conductivity for an infinite one-dimensional system. Moreover. for the half-filled band case, we establish a metal-insulator quantum phase transition by analysing the particle-particle/boson correlations and photoemission spectra.