Importance of exchange contributions to scattering and screening in the quantum kinetic regime

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Wolterink, T. ; Axt, Vollrath Martin ; Kuhn, Tilmann:
Importance of exchange contributions to scattering and screening in the quantum kinetic regime.
In: Long, A. R. ; Davies, J. H. (Hrsg.): Physics of semiconductors 2002 : proceedings of the 26th International Conference on the Physics of Semiconductors held in Edinburgh, UK, 29 July - 2 August 2002. - Bristol : Institute of Physics , 2003 . - CD-ROM, P84 . - (Institute of Physics Conference Series ; 171 )
ISBN 0-7503-0924-5

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Abstract

We study the role of exchange contributions for the ultrafast carrier relaxation in the quantum kinetic regime. The analysis is based on a density matrix approach where besides the direct contributions to Coulomb scattering and screening in the random phase approximation (RPA) also the corresponding exchange terms are included which are necessary to satisfy the correct antisymmetry of the two-particle density matrix. At early times we find significant deviations from the commonly used RPA where these exchange contributions are neglected. At later times exchange contributions to scattering and screening tend to compensate each other and the differences between RPA and the calculations including exchange are reduced.