Abstract

  Quantum coherence plays a key role in light-harvesting exciton transfer and charge mobility of organic semi-conductors, and will be the focus of this talk. 

  (1) The transfer process in between LH2 rings is dramatically enhanced by the coherence resulting from the 9-fold ring symmetry, which will be explained by the minimal frustration consideration.  Further, we have developed a numerically exact method based on stochastic path integrals (sPI) to predict emission spectra and generalized Forster rate of molecular aggregates and found that the enhanced rate in LH2 is 9ps without disorder and around 20ps with disorder, consistent with experimental measurements.

  (2) We have studied coherent quantum transport in disordered systems and showed an optimal diffusion constant at an intermediate level of noise/temperature. Detailed calculations indicate the crucial role of coherence length and predict charge mobility in organic semi-conductors close to experimental values.  Further, we have explored 1D-2D transition in the diffusion of nanotubes and the possibility of ballistic dynamics in 2-D dipolar lattices.