Biexciton effects in femtosecond nonlinear transmission of semiconductor quantum dots

The dynamics of carrier-induced absorption changes in CdSe quantum dots are investigated with femtosecond spectroscopy. After excitation with 4-eV photons a redshift of the lowest optical transition is observed in the initial phase of carrier relaxation. This shift is attributed to a biexciton effect where two electron-hole pairs interact via the Coulomb potential.