Temperature relaxation in dense two-temperature plasmas

Complete text of publication follows. We present a quantum kinetic approach for the energy and temperature relaxation in strongly coupled plasmas. Starting from the quantum version of the BBGKY-hierarchy, we derive a balance equation for the total energy. With this approach, the problem of the division of the electron-ion part of the potential energy is solved. The right hand side of the balance equation includes a quite general expression for the energy transfer rate in terms of the correlation function of density fluctuations. By applying well-known approximation schemes for the density fluctuations, it is now possible to derive different expressions for the electron-ion energy transfer such as the Fermi Golden Rule (FGR) or Coupled Mode (CM) formulae. Furthermore, it becomes possible to systematically improve the level of approximation for the energy transfer rates based on the real-time Green's function formalism. For numerical evaluation, we apply here density response functions taken in random phase approximation and with static local field corrections. On this basis, the relaxation of the total energy in dense two-component plasmas is then investigated numerically. The heat capacity of the electron subsystem is derived using a perturbation expansion in the imaginary time Green's function formalism. The ion heat capacity is calculated using techniques of classical statistics (HNC). It is shown that coupled collective modes can reduce the electron-ion energy transfer under certain conditions; typically in the beginning of the relaxation process. We study the quantitative effects of ionic correlations, electron degeneracy and collective modes on the final temperature and on the relaxation time. The comparison of our results to recent computer simulations and to experiments shows agreement in certain limiting cases but differences in the relaxation process and relaxation time. Reasons for deviations from published results are discussed.