Extended star graph as a light-harvesting-complex prototype: Excitonic absorption speedup by peripheral energy defect tuning

We study the quantum dynamics of a photoexcitation uniformly distributed at the periphery of an extended star network (with NB branches of length LB). More specifically, we address here the question of the energy absorption at the core of the network and how this process can be improved (or not) by the inclusion of peripheral defects with a tunable energy amplitude ??. Our numerical simulations reveal the existence of optimal value of energy defect A??? which depends on the network architecture. Around this value, the absorption process presents a strong speedup (i.e., reduction of the absorption time) provided that LB LB??? with LB??? ??? 12.5/ ln(NB). Analytical and numerical developments are then conducted to interpret this feature. We show that the origin of this speedup takes place in the hybridization of two upper-band excitonic eigenstates. This hybridization is important when LB LB??? and vanishes almost totally when LB > LB???. These structural rules we draw here could represent a potential guide for the practical design of molecular nanonetwork dedicated to the realization of efficient photoexcitation absorption.

Automated summary

This study investigates the energy absorption of photoexcitation at the core of a star network, which is distributed uniformly at the periphery. The existence of an optimal value of energy defect is revealed, which depends on the network architecture. When certain conditions are met, the absorption process can be accelerated. The findings of this study may serve as a potential guide for the design of efficient molecular nanonetworks for photoexcitation absorption.