Engineering directed excitonic energy transfer

Abstract

We provide an intuitive platform for engineering exciton transfer dynamics. We show that careful consideration of the spectral density, which describes the system-bath interaction, leads to opportunities to engineer the transfer of an exciton. Since excitons in nanostructures are proposed for use in quantum information processing and artificial photosynthetic designs, our approach paves the way for engineering a wide range of desired exciton dynamics. We carefully describe the validity of the model and use experimentally relevant material parameters to show counter-intuitive examples of a directed exciton transfer in a linear chain of quantum dots.The widely-applied Förster theory for energy transfer links experimental results to estimates of system information, particularly in biological and nanoscale applications [1,2]. The usefulness of this theory is partly due to the simple expression of the kinetic rate constants as a product of electronic coupling and a spectral overlap factor which captures the complexity of the environment. Förster theory describes transport in the incoherent limit, but a complementary and more elaborate approach, such as Redfield theory, is often required to describe energy transfer. However, the information essential to understanding the dynamics is buried within the structure of the equations. In this letter, we employ a quantum kinetic rate approach to distill the information contained in equations into a simple, yet instructive, formula. We use this approach to design directed exciton transfer mediated by an environment.Excitonic energy transfer (EET) has been studied in systems as varied as quantum dot (QD) nanostructures [3,4], polymer chains [5], and photosynthetic complexes [6,7]. Many applications of EET would benefit from controlling exciton dynamics. Perfect state transfer, as studied in the quantum computing community, is achievable in certain engineered systems, but only at particular times during coherent evolution [8]. Recent works have shown that environment-induced decoherence can alter exciton dynamics [9][10][11], although controlling the transfer direction has only been achieved using external potentials [12]. Our paper builds upon the idea of engineering exciton transfer by designing appropriate system-bath interactions [13,14]. We show that it is possible to design experimentally realizable systems where the environment can be used to direct the flow of energy.The Hamiltonian used in our simulation aims to capture dynamics in a single-exciton manifold [15] interacting with an environment,This representation is in the site basis {|s n } of localized excitations on each of N sites, (e.g. QDs or chromophores), with excitation energy E n for each site and inter-site coupling J mn . The environment is described by a phonon bath,Ĥwhere b † q (b q ) is the creation (destruction) operator for a phonon with wavevector q. The system-bath interaction is assumed to be linear,where g n q describes the site-specific coupling of electronic and vibrational degrees of freedom. We ...

Quantum dynamics of a vibronically coupled linear chain using a surrogate Hamiltonian approach

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Coherent excitation transfer via the dark-state channel in a bionic system

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