Subband Renormalization in the Presence of a Dense Electron-Hole Plasma in a Quantum-Well

We calculate the shrinkage of the gaps between the two lowest subbands in a quantum well induced by the presence of a photo-excited electron-hole plasma. The results are reported as a function of well width and plasma concentration. The reduction of the higher gaps is found to be almost as strong as that of the fundamental gap. The contribution of the so called 'off-diagonal' terms is shown to be important.