Dynamics of exciton-polaron transition in molecular assemblies: The variational approach

Abstract

Dynamics of excitonic polaron formation in molecular systems coupled to an overdamped bath are investigated using the Dirac-Frenkel variational principle and Davydov D1 Ansatz. Using a two-site model system we show that a few qualitatively distinct relaxation regimes of an optically created exciton are possible, depending on the timescale of bath fluctuations. A slow bath always leads to adiabatic polaron formation. Non-adiabatic exciton self-trapping occurs when the system is strongly coupled to a fast bath. Weak coupling to such bath does not perturb the excitonic picture. The complex system-bath dynamics can then be mapped to an effective model where the resonant coupling between sites is quenched during relaxation. The timescale of the polaron formation can be defined by the timescale of resonant coupling quenching, and is found to directly correlate with the bath relaxation time.

From wavelike to sub-diffusive motion: exciton dynamics and interaction in squaraine copolymers of varying length

“…The current paradigm is that after photoexcitation the excitonic states are established, possibly with accompanying polaron formation. 57 The excitons then diffuse by a classical random walk through the polymer. 5 While separately the diffusive transport and wavelike motion have been described, how the former emerges from the latter is a subject under debate, 56 typically ignored when discussing the exciton migration.…”

Dynamics of exciton polaron in microtubule

“…The analysis performed here shows that the interaction electron-phonon coupling results in the formation of large polarons, and these are responsible for high-frequency conductivity in magnetite. Chorošajev et al (2014) studied the dynamics of the formation of polaron excitons in molecular systems coupled to an overamplified bath using the Dirac-Frenkel variational principle and the Davydov Ansatz D1. They showed that the timescale of the polaron formation can be defined by the timescale of resonant coupling quenching.…”

Temperature Controlled Open Quantum System Dynamics using Time-dependent Variational Method

“…Obtaining dynamics of open quantum systems, i.e., quantum systems that are identified as separate from its environment, yet remain in thermal contact with it, is one of the most general quantum mechanical problems. Its applicability range from excited state relaxation in optical response [1,2], energy transport in molecular aggregates [3][4][5][6][7][8], photosynthetic complexes [9][10][11][12] and others [13][14][15][16][17]. Prevalent theoretical description is given in terms of system-bath model in constant temperature bath conditions [18,19], where the system degrees of freedom are coupled to the bath-induced thermal fluctuations representing the environment, e.g., phonons or vibrational motion of surrounding molecules.…”