We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
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21 December 2013
Research Article|
December 17 2013
Origin of long-lived oscillations in 2D-spectra of a quantum vibronic model: Electronic versus vibrational coherence
M. B. Plenio;
M. B. Plenio
Institute for Theoretical Physics, Albert-Einstein-Allee 11,
University Ulm
, D-89069 Ulm, Germany
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J. Almeida;
J. Almeida
Institute for Theoretical Physics, Albert-Einstein-Allee 11,
University Ulm
, D-89069 Ulm, Germany
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S. F. Huelga
S. F. Huelga
Institute for Theoretical Physics, Albert-Einstein-Allee 11,
University Ulm
, D-89069 Ulm, Germany
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J. Chem. Phys. 139, 235102 (2013)
Article history
Received:
September 05 2013
Accepted:
November 26 2013
Citation
M. B. Plenio, J. Almeida, S. F. Huelga; Origin of long-lived oscillations in 2D-spectra of a quantum vibronic model: Electronic versus vibrational coherence. J. Chem. Phys. 21 December 2013; 139 (23): 235102. https://doi.org/10.1063/1.4846275
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