Dear Alan,

I've attached a version of the biexciton paper that we submitted to Science awhile back and that has been languishing as I have been too swamped to fix it in the way they requested, which includes making it longer and more accessible to both the nonlinear spectroscopy and semiconductor exciton communities. That said, it will likely be very accessible to you and your group members, especially if you've been looking at Graham Fleming's recent work.

As for the plans for coherent experiments, I have not written them up cogently but I can describe them to you in a nutshell. Basically we can make this same class of 2D measurement on organic samples that will be fabricated in the project, e.g. multilayer J-aggregate films made by Vladimir Bulovic, so that we can see directly the dynamics of coherence and energy transport. This is important generally to provide feedback on how the fabrication is going, and more fundamentally to understand the connection between structure and dynamics. A key part of this is to look for any signs of coherence in the dynamics, similar to what Fleming has seen, evidenced in oscillatory time-dependent amplitudes of off-diagonal peaks in the 2D spectrum. We also should see the extent of inhomogeneity and how that influences the dynamics. And seeing biexciton coherences as we do in the semiconductor case could reveal higher-order electron correlations that may be important for a comprehensive description of the electronic structure.

Professor Keith A. Nelson       Tel: 617-253-1423