Excitonic Approach to Ultrafast Optical Response of Semiconductors

An excitonic approach to treating the coherent dynamics of optically generated charge carriers in semiconductor nanostructures is presented in this work. The main feature of this approach is that it includes exchange interactions and phase space filling effects, which have generally been omitted in previous excitonic treatments of coherent dynamics, so that it can go beyond the low excitation limit. In contrast to the well-known semiconductor Bloch equations, this approach treats intraband correlations without factorization. The excitonic formalism and the obtained excitonic equations are shown to be particularly advantageous in systems where bound excitons dominate the optical response and where intraband correlations play a central role. The excitonic formalism presented here is an efficient approach that can be applied in a wide range of systems, which makes it a potential alternative to the standard semiconductor Bloch equations for many systems where the intraband correlations are crucial.