Exciton diffusion length in complex quantum systems: the effects of disorder and environmental fluctuations on symmetry-enhanced supertransfer
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Lloyd_Exciton diffusion.pdf
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Author(s)
Abasto, D. F.
Mohseni, Masoud
Lloyd, Seth
Zanardi, P.
Alternative Title
Exciton diffusion length in complex quantum systems: the effects of disorder and environmental fluctuations on symmetry-enhanced supertransfer
Date Issued
July 2012
Journal
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Publisher
Royal Society, The
Citation
Abasto, D. F., M. Mohseni, S. Lloyd, and P. Zanardi. Exciton Diffusion Length in Complex Quantum Systems: The Effects of Disorder and Environmental Fluctuations on Symmetry-enhanced Supertransfer. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1972 (July 2, 2012): 3750-3770.
Version
Author's final manuscript
Abstract
Symmetric couplings among aggregates of n chromophores increase the transfer rate of excitons by a factor n2, a quantum-mechanical phenomenon called ‘supertransfer’. In this work, we demonstrate how supertransfer effects induced by geometrical symmetries can enhance the exciton diffusion length by a factor n along cylindrically symmetric structures, consisting of arrays of rings of chromophores, and along spiral arrays. We analyse both closed-system dynamics and open quantum dynamics, modelled by combining a random bosonic bath with static disorder. In the closed-system case, we use the symmetries of the system within a short-time approximation to obtain a closed analytical expression for the diffusion length that explicitly reveals the supertransfer contribution. When subject to disorder, we show that supertransfer can enhance excitonic diffusion lengths for small disorders and characterize the crossover from coherent to incoherent motion. Owing to the quasi-one-dimensional nature of the model, disorder ultimately localizes the excitons, diminishing but not destroying the effects of supertransfer. When dephasing effects are included, we study the scaling of diffusion with both time and number of chromophores and observe that the transition from a coherent, ballistic regime to an incoherent, random-walk regime occurs at the same point as the change from supertransfer to classical scaling.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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Creative Commons Attribution-Noncommercial-Share Alike 3.0
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DOI of Published Version
https://doi.org/10.1098/rsta.2011.0213
