Trion oscillator strength

Our new commutation technique for excitons interacting with electrons allowed us to derive the X− trion expansion in terms of exciton–electron pairs while taking exactly into account the fact that the exciton can be made with any of the two electrons. We use this expansion to calculate the trion oscillator strength and to identify the physics which controls its reduction from the exciton value. We also discuss the state of the art of trion absorption in doped semiconductors.