Dynamics of coherence, localization and excitation transfer in disordered nanorings

Somoza, Alejandro D.; Sun, Kewei; Molina, Rafael A.; Zhao, Yue

doi:10.1039/c7cp03171h

Cited by 11 publications

(5 citation statements)

References 92 publications

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“…Since the sunlight is very dilute, usually only one excitation is present in such complexes, so that single-excitation delocalized states are usually investigated. Delocalized excitonic states can lead to cooperative effects, such as superradiance [9,10,22,[26][27][28][29] and super-transfer [30,31], and they can be useful in both natural or artificial light-harvesting complexes [19,28,[32][33][34][35][36][37][38][39][40][41][42][43]. Specifically, coherently delocalized excitonic states can have a large dipole strength which strongly couples them to the electromagnetic field (EMF).…”

Section: Introductionmentioning

confidence: 99%

Macroscopic coherence as an emergent property in molecular nanotubes

et al. 2019

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Nanotubular molecular self-aggregates are characterized by a high degree of symmetry and they are fundamental systems for light-harvesting and energy transport. While coherent effects are thought to be at the basis of their high efficiency, the relationship between structure, coherence and functionality is still an open problem. We analyse natural nanotubes present in Green Sulphur Bacteria. We show that they have the ability to support macroscopic coherent states, i.e. delocalized excitonic states coherently spread over many molecules, even at room temperature. Specifically, assuming a canonical thermal state we find, in natural structures, a large thermal coherence length, of the order of 1000 molecules. By comparing natural structures with other mathematical models, we show that this macroscopic coherence cannot be explained either by the magnitude of the nearest-neighbour coupling between the molecules, which would induce a thermal coherence length of the order of 10 molecules, nor by the presence of long-range interactions between the molecules. Indeed we prove that the existence of macroscopic coherent states is an emergent property of such structures due to the interplay between geometry and cooperativity (superradiance and super-transfer). In order to prove that, we give evidence that the lowest part of the spectrum of natural systems is determined by a cooperatively enhanced coupling (super-transfer) between the eigenstates of modular sub-units of the whole structure. Due to this enhanced coupling strength, the density of states is lowered close to the ground state, thus boosting the thermal coherence length. As a striking consequence of the lower density of states, an energy gap between the excitonic ground state and the first excited state emerges. Such energy gap increases with the length of the nanotube (instead of decreasing as one would expect), up to a critical system size which is close to the length of the natural complexes considered.

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Section: Introductionmentioning

confidence: 99%

Macroscopic coherence as an emergent property in molecular nanotubes

et al. 2019

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“…Only the electronic ground-state normal modes are represented by the coherent states, and modes of the excited state are expanded in terms of the ground-state coherent states. Davydov-type wave functions have been extensively used to model a single molecule, as well as their aggregate dynamics, − linear and nonlinear spectra. − …”

Section: Theoretical Methodsmentioning

confidence: 99%

Simulation of Ab Initio Optical Absorption Spectrum of β-Carotene with Fully Resolved S₀ and S₂ Vibrational Normal Modes

et al. 2022

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The electronic absorption spectrum of β-carotene (β-Car) is studied using quantum chemistry and quantum dynamics simulations. Vibrational normal modes were computed in optimized geometries of the electronic ground state S 0 and the optically bright excited S 2 state using the time-dependent density functional theory. By expressing the S 2-state normal modes in terms of the ground-state modes, we find that no one-to-one correspondence between the ground- and excited-state vibrational modes exists. Using the ab initio results, we simulated the β-Car absorption spectrum with all 282 vibrational modes in a model solvent at 300 K using the time-dependent Dirac–Frenkel variational principle and are able to qualitatively reproduce the full absorption line shape. By comparing the 282-mode model with the prominent 2-mode model, widely used to interpret carotenoid experiments, we find that the full 282-mode model better describes the high-frequency progression of carotenoid absorption spectra; hence, vibrational modes become highly mixed during the S 0 → S 2 optical excitation. The obtained results suggest that electronic energy dissipation is mediated by numerous vibrational modes.

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“…It models dynamics of both the system and the bath vibrational DOFs approximatelly by representing vibrational states using coherent states (CSs). Accuracy of the technique have been shown to improve by considering more general variants of the Davydov D 2 ansatz, i.e., D 1 ansatz [38] or by using intermediatelly complex D 1.5 ansatz [39]. Still, the greatest improvement came by considering a trial wavefunction made of a linear superposition of Davydov D 2 ansatz (multi-D 2 ) and its more complex multi-D 1 variant [40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Modeling irreversible molecular internal conversion using the time-dependent variational approach with sD₂ ansatz

Jakučionis

Mančal

Abramavičius

2020

Phys. Chem. Chem. Phys.

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Effects of non-linear coupling between the system and the bath vibrational modes on the system internal conversion dynamics are investigated using the Dirac-Frenkel variational approach with the defined sD2 ansatz. It explicitly accounts for the entangled system electron-vibrational wavepacket states, while the bath quantum harmonic oscillator (QHO) states are expanded in a superposition of coherent states (CS). Using a non-adiabatically coupled three-level model, we show that quadratic system-bath coupling induces non-reversible internal conversion when the bath QHO wavepacket representation is highly non-Gaussian. The quadratic coupling results in a broadened and asymmetrically squeezed bath QHO wavepackets in the coordinate-momentum phase space. Additionally, we found that computational effort can be reduced using degenerate CSs to represent the initial bath wavepackets.

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Dynamics of coherence, localization and excitation transfer in disordered nanorings

Cited by 11 publications

References 92 publications

Macroscopic coherence as an emergent property in molecular nanotubes

Macroscopic coherence as an emergent property in molecular nanotubes

Simulation of Ab Initio Optical Absorption Spectrum of β-Carotene with Fully Resolved S₀ and S₂ Vibrational Normal Modes

Modeling irreversible molecular internal conversion using the time-dependent variational approach with sD₂ ansatz

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Dynamics of coherence, localization and excitation transfer in disordered nanorings

Cited by 11 publications

References 92 publications

Macroscopic coherence as an emergent property in molecular nanotubes

Macroscopic coherence as an emergent property in molecular nanotubes

Simulation of Ab Initio Optical Absorption Spectrum of β-Carotene with Fully Resolved S0 and S2 Vibrational Normal Modes

Modeling irreversible molecular internal conversion using the time-dependent variational approach with sD2 ansatz

Contact Info

Product

Resources

About

Simulation of Ab Initio Optical Absorption Spectrum of β-Carotene with Fully Resolved S₀ and S₂ Vibrational Normal Modes

Modeling irreversible molecular internal conversion using the time-dependent variational approach with sD₂ ansatz