Transfer and Decay of an Exciton Coupled to Vibrations in a Dimer

TL;DR

This paper investigates how an exciton coupled to vibrations in a dimer transfers and decays, revealing how different vibrational speeds affect dynamics, including nonlinear trapping, decay rates, and complex behaviors.

Contribution

It provides an analytical explanation of exciton-vibration dynamics in a dimer, including effects of decay sinks and new dynamic phenomena beyond previous approximations.

Findings

Fast vibronic subsystem enhances nonlinear self-trapping.

Large coupling slows exciton decay.

Transition regime exhibits complex, possibly chaotic dynamics.

Abstract

Transfer and decay dynamics of an exciton coupled to a polarization vibration in a dimer is investigated in a mixed quantum-classical picture with the exciton decay incorporated by a sink site. Using a separation of time scales, it is possible to explain analytically the most important characteristics of the model. If the vibronic subsystem is fast, these are the enhancement of nonlinear self trapping due to the sink and the slowing down of the exciton decay for large coupling or sink strength. Numerical results obtained recently for the DST approximation to the model are quantitatively explained and new dynamic effects beyond this approximation are found. If the vibronic subsystem is slow, the behavior of the system follows closely the predictions of the adiabatic approximation. In this regime, the exciton decay crucially depends on the initial conditions of the vibronic subsystem. In the transition regime between adiabatic and DST approximation, complex dynamics is observed by numerical computation. We discuss the correspondence to the chaotic behavior of the excitonic-vibronic coupled dimer without trap.