Memory-function approach to interacting quasiparticle boson systems

The fundamental problem of the effects of strong interactions with lattice vibrations on quasiparticle transport is analyzed with the help of the memory-function approach introduced many years ago in the context of exciton and charge transport in molecular aggregates. Comparison is made among the exact evolution in a simplified system, the predictions of the memory approach, and evolution based on semiclassical arguments. It is shown that, for a number of physically relevant parameter ranges, the memory approach provides an excellent representation of the exact evolution while the semiclassical approach does not. A quantum yield experiment appropriate to sensitized luminescence is examined in the light of the tract evolution and the various approximations. Three physical systems are also discussed. They involve charge transport in aromatic hydrocarbon crystals, thermal conduction in refractory materials, and vibrational energy transfer in biological systems.