Quantum interference in semiconductor quantum wells

We present a review of theoretical and experimental evidence for quantum in terference in intersubband transitions of coupled semiconductor quantum wel ls. Intersubband absorption spectra are calculated using semiconductor Bloc h equations to include the Coulomb interaction between the conduction band electrons. We demonstrate that the absorption spectra must be viewed as col lective excitations. In a configuration analogous to electromagnetically in duced transparency (EIT) in atomic systems, we show that quantum interferen ce occurs between the levels of these collective intersubband excitations r ather than single electronic states. Experiments which demonstrate quantum interference in coupled quantum wells due to tunneling induced transparency (TIT) are presented. The design issues for such samples are reviewed, and the effects of monolayer growth fluctuations on the spectra are simulated. Finally, we discuss the temperature dependence of TIT and demonstrate that the quantum interference persists at room temperature.