Electron-phonon coupling in the two-phonon mode ternary alloy

We have investigated the infrared transmission of a two-dimensional electron gas (2DEG) confined in a $\chem{Al_{0.25}In_{0.75}As/Ga_{0.25}In_{0.75}As}$ single quantum well in order to study the electron optical phonon interaction in a two-phonon mode system. Infrared transmission experiments have been performed in both the perpendicular Faraday (PF) and tilted Faraday (TF) configurations for which the growth axis of the sample is tilted with respect to the incident light propagation direction and to the magnetic-field direction. The experimental results lead to question the validity of the concept of polaron mass in a real material