Exciton Superradiance and Coherence.

J. Goll, Hermann Haken

Kikuo Cho

Eiichi Hanamura, Tetsuji Tokihiro, Yoshihiro Manabe

V.M. Agranovich, Shaul Mukamel

Y C Lee, K C Liu

The theory of superradiance of excitons in thin crystal films is presented. While the broken crystal symmetry in the direction normal to the film plane renders the radiative decay of the exciton possible, the remaining crystal symmetry on the film leads to phase coherence between the exciton and the photon fields everywhere on the film. Consequently, a trading between the degrees of freedom of the radiation field and those of the atoms is shown to be responsible for the predicted superradiative enhancement of the exciton decay by a factor ( lambda /d) 2 >>1 in the optical region.

Gunnar G. Bjork, Stanley Pau, Joseph M. Jacobson +2 more

Quantum-well exciton superradiance and exciton cavity polarization formation both require a substantial spatial coherence area in order to become the dominant exciton field interaction. In both interaction processes the quantum-well (in-plane) momentum is conserved. Momentum scattering, which is due, e.g., to interaction with a phonon reservoir, quickly localizes an initially delocalized exciton and randomizes the excitation momentum. We take a close look at how momentum scattering influences measurements of excitonic superradiance and of exciton cavity polariton splitting. An important conclusion is that, in general, measurements of the emitted light do not correspond to the evolution of the system as a whole. Therefore, e.g., the measured decay rates do not correspond to the true decay rate of the system.