Imaging interferometry of excitons in two-dimensional structures: Can it detect exciton coherence

TL;DR

This paper develops a theoretical framework for imaging interferometry of excitons in two-dimensional structures, revealing that observed interference patterns can arise from incoherent emission, challenging previous interpretations of exciton coherence.

Contribution

The authors derive general expressions for interferometric setups considering partial coherence and show that interference patterns may not indicate exciton coherence, prompting a reexamination of prior experimental conclusions.

Findings

Interference patterns depend on emission patterns and imaging setup.

Observed interference can occur with incoherent emitters.

Previous claims of exciton coherence may need reassessment.

Abstract

Using the theory of imaging with partially coherent light, we derive general expressions for different kinds of interferometric setups like double slit, shift and mirror interference. We show that in all cases the interference patterns depend not only on the point spread function of the imaging setup but also strongly on the spatial emission pattern of the sample. Taking typical experimentally observed spatial emission patterns into account, we can reproduce at least qualitatively all the observed interference structures, which have been interpreted as signatures for spontaneous long range coherence of excitons, already for incoherent emitters. This requires a critical reexamination of the previous work.