Femtosecond spectroscopic signatures of electronic correlations in conjugated polyenes and semiconductor nanostructures

Electronic correlation effects which can be directly probed by ultrafast four-wave mixing are predicted using the electronic-oscillator representation of conjugated polyenes, Comparison with inorganic semiconductors is made possible since the semiconductor Bloch equations projected onto the lowest exciton are obtained as a limiting case. A sign difference in a nonlinear scattering potential clearly shows up in the Wigner spectrogram representing the time and frequency resolved signal.