|Scientific Reports Publication|
Chemistry and Physics Prof. Jin Wang and Physics Graduate Student Zhedong Zhang published "Origin of long-lived quantum coherence and excitation dynamics in pigment-protein complexes" in the Scientific Reports.
Nonequilibrium quantum statistical dynamics is of fundamental importance and critical for understanding of the energy and charge transports. The recent development of renewable energy demands the improvement of efficiency of energy and charge transports in materials. The widespread interests in exploring the quantum nature in solar cells and the antenna systems have been triggered by the experimental investigations of excitonic dynamics in a wide variety of systems, e.g., semiconductors, organic molecules, light harvesting complexes, natural and synthetic photosynthetic complexes. Even with the current knowledge of electronic structure in antenna and the advances in spectroscopy that uncovered the long-lived quantum coherence in fluctuating environment, the full understanding of the role of coherence and the mechanism of excitation energy transfer has still remained elusive.
In this study, a mechanism for a long standing issue of the origin of long-survived quantum coherence (e.g., light-harvesting complexes) for efficient energy transfer was uncovered in a general scenario. The bare electrons are surrounded by nuclear vibrational modes, which leads to the strong exciton-vibron coupling. The new composite called polaron gives rise to the screening and leads to much weaker interactions with the environments. The decoherence will then be significantly suppressed and the long-lived quantum coherence emerges. The nonequilibriumness from detailed balance breaking and coherence can funnel the downhill migration of excitons. The survival of quantum coherence is long enough to significantly improve the energy transfer efficiency under the breakdown of time-reversal symmetry. This result suggesting a mechanism of slowing down the dephasing is of importance for energy/charge transports and quantum information/computing.