Fundamental difference between measured and calculated exciton-phonon coupling in nanostructures

Abstract

Using ab initio density functional theory applied to semiconductor nanoclusters, we show that optical experiments where absorption is involved probe vibrations that are not necessarily the ones with large exciton-phonon matrix elements. The vibrations involved in these experiments must satisfy more stringent symmetry constraints than given by the selection rules of the exciton-phonon matrix elements. This resolves a long-standing observed discrepancy, while offering a viable theoretical approach to properly account for the experimental situation.