Ultrafast tailoring of the exciton distribution in quantum wells

By excitation with two, consecutive, picosecond pulses we demonstrate that the distribution and temperature of a photocreated exciton population in semiconductor quantum wells can be dynamically tailored. The changes in the exciton distribution result in abrupt alterations of the photoluminescence dynamics, in particular in the appearance of a sudden decrease in the heavy-hole excitonic emission when the second pulse impinges upon the sample. We present a quasi-equilibrium thermodynamical model that includes the energy distribution of excitons and electron-hole plasma, which quantitatively accounts for the sharp dips observed in the exciton emission dynamics.