Quantum Coherence in Light-harvesting Systems and Organic Semiconductors
Abstract: We discover surprising consequences of the well-known quantum effects suchas zero-point Quantum coherence is a key concept in chemical physics and will bediscussed in the context of charge mobilitylexciton diffusion in organicsemiconductors and energy transfer in light-harvesting complexes. I. Coherent quantum transport in disordered systems displays an optimaldiffusion constant at an intermediate level of noise and temperature. Detailedcalculations indicate the crucial role of localization length in coherent transport andpredict charge mobility close to experimental values. Further, we have explored thesubtle dependence of the diffusion constant on the dimensionality and shape of thesample and demonstrated the universal scaling of the 1D-2D transition in nanotubes. II. Forster energy transfer theory has been extended to multi-chromophoric(MC) systems by incorporating the correlation between exciton and its environments.This correlation leads to the rotation of the reduced density matrix and is fullycounted in two recently-developed methods: numerically exact stochastic pathintegrals (SPI) and theoretically self-consistent coherent potential approximation(CPA). Application of these methods demonstrates incoherent hopping in FMO andcoherent transfer in LH2.About the reporter: Jianshu Cao is a professor of chemistry at MIT. He received a Ph. D. in physics fromColumbia University in 1993, under the direction of Bruce Berne. After postdoctoral researchwith Greg Voth at University of Pennsylvania and with late Kent Wilson at UCSD, he jointedthe MIT faculty in 1998. He is primarily known for his work on open quantum dynamics andsingle molecule kinetics. His current research program consists of two major components: (i)the development of theoretical and computational methods to model quantum dynamics inlight-harvesting systems, organic semiconductors, and quantum devices, and (ii) theanalysis of non-equilibrium chemical kinetics and its im plications in biophysical processes. Over the last five years, (Jan. 2013-Ja. 2018). his group published a total of 56 papers,including 5 in Physical Review Letters, 1 in PNAS, 5 in JPC Letters, 3 in Scientific Reports, 3in Nano Letters, and 2 in Nature Communications (collaborations) 20% of thesepublications are collaborative. In addition, Jianshu Cao is actively involved in the scientificcommunity, attending meetings, organizing conferences, serving on editorial boards, andparticipating in stude ntlscholar exchange programs.