Far-infrared magnetospectroscopy of polaron states in self-assembled InAs/GaAs quantum dots

We investigate the far infrared magneto-optical transitions in self-assembled InAs quantum dots with different lateral diameters and we show that a purely electronic model is unable to account for the experimental data. We calculate the coupling between the mixed electron-LO-phonon states using the Fr\"ohlich Hamiltonian, from which we determine the polaron states as well as the energies of the dipolar electric transitions. The excellent agreement between the experiments and the calculations obtained for the different samples provides strong evidence that the magneto-optical transitions arise between polaron states and that the electrons and LO phonons experience a strong coupling regime.