J. Phys. IV France 10 (2000) Pr5-161-Pr5-165
Theory of quadratic responseG.J. Kalman1 and J.M. Rommel1, 2
1 Department of Physics, Boston College, Chestnut Hill, MA 02167, U.S.A.
2 SemiTest Inc., Billerica, MA 01821, U.S.A.
While the theory of linear response functions in many body theory has developed into a substantial lore over the past decades, rather little is known about the properties and behavior of higher order (quadratic, etc.) response functions of many body systems. In this poster we first review essential elements of quadratic response theory such as the quadratic fluctuation dissipation theorems and sum rules for the quadratic density response function. Next we show how the correlational local field G(k,ω) in the linear response is fundamentally linked to the quadratic response function which opens a way to a non-perturbational analysis of the former. We proceed to present the results of the explicit calculation of the quadratic density response of 2D and 3D electron gas. Both, real and imaginary part of the latter reveal an extremely rich behavior. Of particular interest is the comparison between the two- and the three-dimensional case.
© EDP Sciences 2000