Showing papers by "Áurea R. Vasconcellos published in 1992"

Nonlinear effects in the production of highly photoexcited polar vibrations.

Abstract: We consider how dissipative nonlinear processes influence the photoproduction of optical phonons in n-doped polar semiconductors. It is shown that such nonlinear effects may lead to interesting and remarkable results. First we show that through free-carrier absorption processes LO phonons in excess of equilibrium are produced in a small off-center region of reciprocal space. Next we show that nonlinear relaxation effects are unimportant at weak to intermediate laser intensities but come to play a role in the range of strong excitations

On the statistical thermodynamics of a model for non-equilibrium semiconductors

Abstract: We describe the non-equilibrium thermodynamics of a model for semiconductors under high levels of excitation using the non-equilibrium statistical operator method. We obtain thermodynamic functions in terms of thermodynamic variables that are accessible to experimental measurements via ultrafast laser spectroscopy. Calculations of entropy production and the rate of entropy production are performed. Kinetic equations for the relaxation processes are derived and Onsager-like coefficients are defined. It is shown that for the system we consider Prigogine's theorem of minimum entropy production holds even in the non-linear regime, and the Glansdorff-Prigogine universal evolution criterion is verified.