Electronic excitation dynamics in multichromophoric systems described via a polaron-representation master equation

Kolli, Avinash; Nazir, Ahsan; Olaya-Castro, Alexandra

doi:10.1063/1.3652227

Cited by 124 publications

(169 citation statements)

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“…However, for natural light-harvesting structures an intermediate strength interaction between the electronic excitations and the high-frequency BChl vibrational modes of the range of 1600 − 2000 cm −1 has been suggested [79][80][81]. In order to account for this effect polaron models have been proposed [35,82,83]. In general, a strong coupling between the exciton and vibrations renormalizes the exciton energy and also reduces its mobility.…”

Section: Discussionmentioning

confidence: 99%

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

et al. 2014

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We present a theoretical study of excitation dynamics in the chlorosome antenna complex of green photosynthetic bacteria based on a recently proposed model for the molecular assembly. Our model for the excitation energy transfer (EET) throughout the antenna combines a stochastic time propagation of the excitonic wave function with molecular dynamics simulations of the supramolecular structure, and electronic structure calculations of the excited states. We characterized the optical properties of the chlorosome with absorption, circular dichroism and fluorescence polarization anisotropy decay spectra. The simulation results for the excitation dynamics reveal a detailed picture of the EET in the chlorosome. Coherent energy transfer is significant only for the first 50 fs after the initial excitation, and the wavelike motion of the exciton is completely damped at 100 fs. Characteristic time constants of incoherent energy transfer, subsequently, vary from 1 ps to several tens of ps. We assign the time scales of the EET to specific physical processes by comparing our results with the data obtained from time-resolved spectroscopy experiments.

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Section: Discussionmentioning

confidence: 99%

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

et al. 2014

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“…3(b). Recently developed methods [15] for spin-boson dynamics can readily be applied to reveal similar insight into manysite systems as previous approaches [21,36] have revealed in the simplest two-site case.…”

Section: Fig 3 (Color Online)mentioning

confidence: 96%

“…While the J-C model is sufficient to study small atom-field coupling, the RWA breaks down at large coupling [9,10] Many-site spin-boson interaction, e.g. multi-state atom-cavity interaction [14] or excitation energy transfer in multi-chromophoric systems [15], continues to be a subject of significant interest, dictating a need for extensions of the two-state model. Extensions of the J-C model have been studied extensively [16][17][18][19], but are no longer applicable in the strong-coupling regime.…”

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confidence: 99%

Quantum Rabi Model forN-State Atoms

Albert

2012

Phys. Rev. Lett.

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A tractable N -state Rabi Hamiltonian is introduced by extending the parity symmetry of the two-state model. The single-mode case provides a few-parameter description of a novel class of periodic systems, predicting that the ground state of certain four-state atom-cavity systems will undergo parity change at strong coupling. A group-theoretical treatment provides physical insight into dynamics and a modified rotating wave approximation obtains accurate analytical energies. The dissipative case can be applied to study excitation energy transfer in molecular rings or chains. Interactions between spin systems and harmonic oscillators (boson modes) have been studied for over 70 years [1][2][3]. One of the most well-known, the quantum Rabi model [1], is a phenomenological Hamiltonian describing interactions between a two-level system and a cavity mode. The model has also formed a basis of understanding for exciton-phonon interactions [4] and, along with its multi-mode extension, has numerous established applications in chemistry and physics (see [5][6][7] and refs. therein). The Jaynes-Cummings (J-C) [3] model is obtained by taking the Rabi model in the rotating wave approximation (RWA), where the "counter-rotating" terms are ignored (see e.g. [8]). While the J-C model is sufficient to study small atom-field coupling, the RWA breaks down at large coupling [9,10] Many-site spin-boson interaction, e.g. multi-state atom-cavity interaction [14] or excitation energy transfer in multi-chromophoric systems [15], continues to be a subject of significant interest, dictating a need for extensions of the two-state model. Extensions of the J-C model have been studied extensively [16][17][18][19], but are no longer applicable in the strong-coupling regime. Exciton-phonon generalizations which extend the parity/reflection symmetry of the Rabi system [20] are neither tractable nor applicable to atom-cavity systems. Most importantly, the Rabi model is the single-mode version of a dissipative (infinite-mode) spin-boson model [21], signifying that light-matter interaction is a simplified manifestation of a more fundamental interaction between a two-state system and a dissipative environment. Previous dissipative [22][23][24][25] generalizations have neither extended the symmetry nor preserved this correspondence. Motivated by these properties, this Letter presents a symmetry-preserving N -state extension of the Rabi model. The extension includes counter-rotating terms in a rigorous, intuitive, and mathematically manageable way, using a minimal number of parameters and paving the way for applications to multi-level atom-cavity experiments at both weak and strong coupling. A grouptheoretical approach [2] provides numerical advantages and physical insight into dynamics of the single-mode case. The symmetric generalized RWA [7] is applied to obtain accurate analytical energies/eigenstates valid for strong coupling. The above procedures are significantly simplified via the generalized spin matrices [26], providing a new tool for the treat...

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“…Realistic models of the exciton dynamics in the FMO complex have to include higher order phonon processes as well as the finite time scale of the reorganization process [17]. This requires to go beyond approximative rate equations [23] and non-perturbative techniques [24][25][26][27][28][29][30] are necessary to study the dissipative transfer dynamics.One key parameter determining the duration of coherent oscillations is the spectral density, which encodes the the mode-dependent exciton-bath coupling. The spectral density has important implications for the two contributions to the decoherence rate γ which is the sum of the relaxation rate γ r and the pure-dephasing rate γ d ([33], ch.…”

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confidence: 99%

Long-Lived Electronic Coherence in Dissipative Exciton Dynamics of Light-Harvesting Complexes

Kreisbeck

Kramer

2012

J. Phys. Chem. Lett.

233

320

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The observed prevalence of oscillatory signals in the spectroscopy of biological light-harvesting complexes at ambient temperatures has led to a search for mechanisms supporting coherent transport through larger molecules in noisy environments. We demonstrate a generic mechanism supporting long-lasting electronic coherence up to 0.3 ps at a temperature of 277 K. The mechanism relies on two properties of the spectral density: (i) a large dissipative coupling to a continuum of higherfrequency vibrations required for efficient transport and (ii) a small slope of the spectral density at zero frequency.PACS numbers: 03.65. Yz, 78.47.nj, 05.60.Gg Long-lasting oscillatory signals in optically excited light-harvesting complexes (LHCs) point towards the prevalence of a coherent electronic dynamics in molecular networks at physiological temperatures [2][3][4][5]. The experiments probe the electronic dynamics using twodimensional (2d) echo-spectroscopy for a series of delaytimes between the excitation pulse and the probe pulse. The 2d spectroscopy makes studies of the dynamics of dissipative systems possible and has found further applications in mesoscopic systems such as molecular nanotubes [6] and semiconductor devices [7]. Due to its known crystallographic structure and relative simplicity, the Fenna-Matthews-Olson (FMO) complex serves as the prototype system for studying the choreography of the energy transfer from the antenna to the reaction center of a light harvesting complex [8]. In 2d spectra long-lasting beatings are observed, ranging from 1.2 ps at T = 150 K to 0.3 ps at T = 277 K [9]. The interplay of coherent dynamics, which leads to a delocalization of an initial excitation arriving at the FMO network from the antenna, and the coupling to a vibronic environment with slow and fast fluctuations, has lead to studies of environmentally assisted transport in LHCs [10,11].An important open question is whether coherence plays a key-role in the functioning of light-harvesting complexes [8]. The theoretical understanding of the experiments is in its early stages and atomistic simulations based on molecular dynamics have not reached agreement [12,13]. A calculation of 2d echo-spectra based on the molecular dynamics simulation [14] does not show clear coherent oscillations at T = 277 K. One key ingredient for efficient transfer dynamics is the strong coupling to vibronic modes, which induces energy dissipation [10,11,15]. For the FMO complex the thermalization occurs within picoseconds and was observed by Brixner et al. by the decay of diagonal-peak amplitudes to lower energies [16]. It has been proposed that the inclusion of the finite time scale of the reorganization process gives rise to long-lasting coherence in LHCs [17]. While a sluggish bath relaxation leads to prolonged population beatings in the FMO network, calculations of 2d echo-spectra show oscillations of the exciton cross-peaks for only about 1/6th of the experimentally recorded time at T = 150 K [18]. For an even longer bath-relaxation cross-peak osci...

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Electronic excitation dynamics in multichromophoric systems described via a polaron-representation master equation

Cited by 124 publications

References 68 publications

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

Quantum Rabi Model forN-State Atoms

Long-Lived Electronic Coherence in Dissipative Exciton Dynamics of Light-Harvesting Complexes

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