Electron–LO-phonon quantum kinetics in semiconductor quantum wells

Quantum correlations between electrons and phonons are demonstrated in two-dimensional semiconductors. The resulting phonon oscillation exhibits characteristic differences with respect to the three-dimensional parent system. We show how these correlations can unambiguously be distinguished from nonequilibrium coherent phonons. Furthermore, coherent control allows separation of the phonon oscillation from another oscillation observed here, specific to two-dimensional systems, which is due to the interference of two electron-electron scattering channels associated with different quantum-well subbands.