THE ENERGY-LOSS RATE AND DYNAMICAL RESISTIVITY OF HOT-ELECTRONS IN SEMICONDUCTORS

Among many proposed field theories for thermal phenomena, thermo-field dynamics (TFD) is a very useful and simple tool to study non-equilibrium many-body systems, especially for a complicated system composed of several subsystems at different thermal equilibria. A complete perturbative calculation scheme in TFD for such systems will be presented. In the TFD method, explicit investigation will be made of the energy loss rate (ELR) and resistivity of hot electrons in semiconductors. Our ELR formula is shown to be different from that obtained by the Keldysh method. The possible ambiguity in the Keldysh method is discussed.