Abstract in Englisch:
Coherent quantum transport in linear and quasi-linear tight-binding models and the influence of decoherence are studied. For the coherent transport description, Green functions and surface Green functions of semi-infinite systems are calculated and the transmission through defects and finite tight-binding chains with and without diagonal disorder are examined. A statistical model based on the division of a large system into coherent subsystems and decoherence regions is analyzed. While on the total system level, classical rate equations interrelate electron energy distribution functions assigned to the decoherence regions, the transition rates themselves are calculated using quantum transport formalism. Thus a two-scale approach is used. For contact Fermi energies within the tight-binding band of the system without disorder, ohmic large scale behavior is observed for any finite density of decoherence regions. If the Fermi energy is outside the band, and for disordered systems, critical decoherence densities are defined. Above the critical densities, material-specific resistivities can be defined. Applying the statistical model for the effects of decoherence on DNA double strands, experimental findings for base-sequence dependent conductance are reproduced.