Eliminating radiative losses in long-range exciton transport

We demonstrate that it is possible to effectively eliminate radiative losses during excitonic energy transport in systems with an intrinsic energy gradient. By considering chainlike systems of repeating "unit"cells that can each consist of multiple sites, we show that tuning a single system parameter (the intra-unit-cell coupling) leads to efficient and highly robust transport over relatively long distances. This remarkable transport performance is shown to originate from a partitioning of the system's eigenstates into energetically separated bright and dark subspaces, allowing long-range transport to proceed efficiently through a "dark chain"of eigenstates. Finally, we discuss the effects of intrinsic dipole moments, which are of particular relevance to molecular architectures, and demonstrate that appropriately aligned dipoles can lead to additional protection against other (nonradiative) loss processes. Our dimensionless open quantum systems model is designed to be broadly applicable to a range of experimental platforms.