Vibronic Enhancement of Algae Light Harvesting

Plants, algae, and photosynthetic bacteria use surprisingly sophisticated optimizations at the quantum mechanical level to harvest the sun's energy. The observation of coherence phenomena within light-harvesting complexes after short laser-pulse excitation has inspired advances in our understanding of light-harvesting optimization, highlighting the interplay of electronic excitations and vibrations. However, it remains unclear how these vibronic effects change or optimize the function of light-harvesting complexes—in other words, what is the design principle we could learn? Here, we use two-dimensional electronic spectroscopy to quantify the vibronic mixing among the light-absorbing molecules of a light-harvesting complex from cryptophyte algae. These data reveal a striking reallocation of absorption strength that, in turn, provides a robust increase in the rate of energy transfer of up to 3.5-fold. The realization of how absorption-strength redistribution, induced by vibronic coupling, provides a multiplicative increase in the rate of energy funneling establishes a bioinspired design principle for optimal light-harvesting systems.