Kuehn, W.; Reimann, K.; Woerner, M.; Elsaesser, T.; Hey, R.; Schade, U.: Strong Correlation of Electronic and Lattice Excitations in GaAs / AlGaAs Semiconductor Quantum Wells Revealed by Two-Dimensional Terahertz Spectroscopy. Physical Review Letters 107 (2011), p. 067401/1-5

Coulomb-mediated interactions between intersubband excitations of electrons in GaAs=AlGaAs double quantum wells and longitudinal optical phonons are studied by two-dimensional spectroscopy in the terahertz frequency range. The multitude of diagonal and off-diagonal peaks in the 2D spectrum gives evidence of strong polaronic signatures in the nonlinear response. A quantitative theoretical analysis reveals a dipole coupling of electrons to the polar lattice that is much stronger than in bulk GaAs, due to a dynamic localization of the electron wave function by scattering processes.