Quantum Transport within a Background Medium: Fluctuations versus Correlations

Abstract

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, groundstate 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.