Through careful theoretical research, scientists at the Center for Excitonics have harnessed decoherence, which bridges quantum mechanics and classical physics approaches to describing the world. This work demonstrates controlled transfer of excitons, tiny mobile concentrations of energy. This breakthrough has far-reaching applications, including artificial photosynthesis, a hot topic in the realm of renewable energy.
Exciton as energy carrier: Excitons in molecules or solids play the essential energy-carrier role. The dynamics of exciton transfer, both within and between molecules, must be controlled to achieve command over artificial photosynthesis, an energy-conversion technology that mimics nature’s evolved method of transforming solar energy into a more usable and storable form. Typically, exciton motion is described by the Förster resonant energy transfer model that describes the process by which an exciton, releasing radiation during collapse, creates another exciton on a neighboring site. On short time scales, however, certain effects, known as coherent quantum effects, not encompassed by FRET can contribute to exciton motion.
Deriving the dynamics of exciton motion: The authors considered these coherent quantum effects with a more detailed theory of exciton dynamics, Redfield theory. Redfield theory shows that engineering decoherence, or the interactions between the exciton and the environment, provides a pathway for controlling exciton motion. Remarkably, the complex dynamics of controlled exciton transfer can be described by an equation that is analogous in form to the better-known and simpler FRET equation.
Moving forward: Applying the findings to a system of three artificial atoms or quantum dots, the scientists have directed the movement of the excitons by tuning properties of the quantum dots and their environment. This work can be used as a framework upon which to build technologies that rely on directed exciton energy transfer.
