Femtosecond Coherent Dynamics of the Fermi Edge Singularity and Exciton Hybrid.pdf

Femtosecond Coherent Dynamics of the Fermi Edge Singularity and Exciton Hybrid T. V. Shahbazyan, N. Primozich, and I. E. Perakis Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 9 9 D. S. Chemla 9 1 t Department of Physics, University of California, Berkeley, CA 94720 and Materials Science c O Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 5 1 2 v Abstract 2 4 3 6 We study theoretically the coherent nonlinear optical response of doped semi- 0 9 conductor quantum wells with several subbands. When the Fermi energy ap- 9 / t a proaches the exciton level of an upper subband, the absorption spectrum ac- m - quires a characteristic double–peak shape originating from the interference be- d n tween the Fermi–edge singularity and the exciton resonance. We demonstrate o c : that, for off–resonant pump excitation, the pump/probe spectrum undergoes v i X a striking transformation in the coherent regime, with a time–dependent ex- r a change of oscillator strength between the Fermi edge singularity and exciton peaks. We show that this effect originates from the many–body electron– hole correlations which determine the dynamical response of the Fermi sea. Possible experimental applications are discussed. PACS numbers: 78.47.+p, 71.10.Ca, 71.45.-d, 78.20.Bh Typeset using REVT X E