Coupling of interface to and lo phonons with electrons in quantum wells and heterojunctions

The eigenvectors of the interface optical phonons and the electron—phonon interaction Hamiltonian, in a trilayer system of polar crystals, are used to discuss the interface optical modes and their coupling with the electrons in single quantum wells and heterojunctions. It is found that the interface phonons have some unexpected properties. In the long-wavelength limit, the transverse vibration occurs at the bulk longitudinal-optical frequencies, while the longitudinal vibration occurs at the transverse-optical frequencies. Both of them are confined, but couple with the electrons everywhere.