We formulate a time-dependent density-matrix functional theory (TDDMFT) approach for higher-order correlation effects like biexcitons in optical processes in solids based on a reduced two-particle density-matrix formalism within the normal orbital representation. A TDDMFT version of the Schrodinger equation for biexcitons in terms of one- and two-body reduced density matrices is derived, which leads to finite biexcitonic binding energies already with an adiabatic approximation. Biexcitonic binding energies for several bulk semiconductors are…
This work has been reported on the Physical Review B [V. Turkowski, C. A. Ullrich, T. S. Rahman, and M. N. Leuenberger, Phys. Rev. B 82 205208 (2010)]