How two-dimensional brick layer J-aggregates differ from linear ones: Excitonic properties and line broadening mechanisms
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Author(s)
Duan, Hong-Guang
Knoester, Jasper
Dijkstra, Arend Gerrit
Nelson, Keith Adam
Cao, Jianshu
Date Issued
April 2016
Journal
The Journal of Chemical Physics
Publisher
American Institute of Physics (AIP)
Citation
Dijkstra, Arend G. et al. “How Two-Dimensional Brick Layer J-Aggregates Differ from Linear Ones: Excitonic Properties and Line Broadening Mechanisms.” The Journal of Chemical Physics 144.13 (2016): 134310. © 2016 AIP Publishing
Version
Final published version
Abstract
We study the excitonic coupling and homogeneous spectral line width of brick layer J-aggregate films. We begin by analysing the structural information revealed by the two-exciton states probed in two-dimensional spectra. Our first main result is that the relation between the excitonic couplings and the spectral shift in a two-dimensional structure is different (larger shift for the same nearest neighbour coupling) from that in a one-dimensional structure, which leads to an estimation of dipolar coupling in two-dimensional lattices. We next investigate the mechanisms of homogeneous broadening—population relaxation and pure dephasing—and evaluate their relative importance in linear and two-dimensional aggregates. Our second main result is that pure dephasing dominates the line width in two-dimensional systems up to a crossover temperature, which explains the linear temperature dependence of the homogeneous line width. This is directly related to the decreased density of states at the band edge when compared with linear aggregates, thus reducing the contribution of population relaxation to dephasing. Pump-probe experiments are suggested to directly measure the lifetime of the bright state and can therefore support the proposed model.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1063/1.4944980
