A MICROSCOPIC TRANSPORT THEORY OF ELECTRON-PHONON SYSTEMS

The two-time Green functions are used to derive kinetic equations of a system of electrons and phonons interacting with Frohlich hamiltonian. A suitable connected diagram analysis is used to derive simultaneous equations similar to Kadanoff-Baym equations. The initial correlations are shown to decay in time comparable to the macroscopic time scale. The general transport equations derived in the steady state are applicable to various transport processes. It is shown that the previous assumption of considering the phonons to be in thermal equilibrium is justified only for dilute systems and phonon drag is appreciable in denser systems