Transport Theory

Abstract

The understanding of transport phenomena transcends the quantum mechanical treatment of isolated systems. Irreversibility and dissipation due to the interaction with another macroscopic system (bath) play here a central role. For their understanding a simple classical, but exactly solvable model of an electron in the presence of a d.c. electric field interacting with classical phonons is helpful. On the other hand, for all practical purposes an intuitive, however, mathematically less sound treatment serves by introducing irreversibility “by hand” in the Boltzmann, Master or rate equations. In this frame the conductivity of electrons scattered on a thermal bath is discussed. Two basic kinds of conduction are considered. That of scattering of freely moving band electrons, typical for metals and semiconductors, as well as that of localized electrons hopping from site to site, typical for disordered systems, like impurity states or amorphous semiconductors. The transverse magneto-resistance in ultra-high magnetic fields also may be understood within this last model. We discuss shortly also the general theory of kinetic coefficients.