Koch, M.M.KochFeldmann, J.J.FeldmannGöbel, E.O.E.O.GöbelThomas, P.P.ThomasShah, J.J.ShahKöhler, KlausKlausKöhler2022-03-032022-03-031993https://publica.fraunhofer.de/handle/publica/18271010.1103/PhysRevB.48.114802-s2.0-0000891320We show by means of time-resolved four-wave-mixing experiments that the simultaneous excitation of energetically distinct and inhomogenously broadened exciton transitions associated with spatially separated quantum-well islands leads to a beating photon echo. This shows that the exciton transitions cannot be described by uncoupled two-level systems. We discuss bleaching, screening, and dipole-dipole interaction as possible coupling mechanisms.enQuantentopfquantum wellstime resolved photoluminescencezeitaufgelöste Photolumineszenz621667530journal article