We propose a three-pulse coherent ultrafast optical technique that is particularly sensitive to two-exciton correlations. Two Liouville-space pathways for the density matrix contribute to this signal which reveals double quantum coherences when displayed as a two-dimensional correlation plot. Two-exciton couplings spread the cross peaks along both axes, creating a characteristic highly resolved pattern. This level of detail is not available from conventional one-dimensional four-wave mixing or other two-dimensional correlation spectroscopy signals such as the photo echo, in which two-exciton couplings show up along a single axis and are highly congested.
@article{arxiv.0712.2263,
title = {Two-dimensional correlation spectroscopy of two-exciton resonances in semiconductor quantum wells},
author = {Lijun Yang and Shaul Mukamel},
journal= {arXiv preprint arXiv:0712.2263},
year = {2009}
}