Abstract
Considering a multi-pathway structure in a light-harvesting complex of photosynthesis, we investigated the role of energy-level mismatches between antenna molecules in transferring the absorbed energy to a reaction center (RC). We found a condition in which the antenna molecules faithfully play their roles: when their effective absorption ratios are larger than those of the receiver molecule directly coupled to the RC. In the absence of energy-level mismatches and dephasing noise, there arises quantum destructive interference between multiple paths that restricts the energy transfer. On the other hand, the destructive interference diminishes as asymmetrically biasing the energy-level mismatches and/or introducing quantum noise of dephasing for the antenna molecules, so that the transfer efficiency is greatly enhanced to nearly unity. Remarkably, the near-unity efficiency can be achieved at a wide range of asymmetric energy-level mismatches. Temporal characteristics are also optimized at the energy-level mismatches where the transfer efficiency is nearly unity. We discuss these effects, in particular, for the Fenna–Matthews–Olson complex.
Highlights
Considering a multi-pathway structure in a light-harvesting complex of photosynthesis, we investigated the role of energy-level mismatches between antenna molecules in transferring the absorbed energy to a reaction center (RC)
In the absence of energy-level mismatches, we show that quantum noise of dephasing, which decreases the quantum coherence of excitation, will never improve the transfer efficiency
|v1 does not contribute to the energy transfer to the RC, so that it states the eventual loss of excitons at the donors
Summary
Where ρ is the density matrix of the molecules and H is the Hamiltonian of the system, given by n n. − j are the raising and lowering operators for molecule j, hj is the excited energy of the molecule and Jjk is the electronic coupling constant between molecules j and k. The first and second non-unitary terms LA(ρ) and LD(ρ) describe the processes of absorbing and emitting thermal light and phonons with coupling constants η j and j at molecule j. The. second term LD(ρ) contains an irreversible decay from the receiver (denoted by j = 1) to the RC with a coupling constant RC. The last non-unitary term LDP(ρ) describes the dephasing process, given by n. J =1 where γ j is the dephasing constant of molecule j This process is caused by the interaction with phonons conserving the system energy. By these non-unitary processes, the system state decoheres. To clarify the principal mechanism, we begin with a single-pathway complex consisting of two antenna molecules and consider a bi-pathway complex of three antenna molecules (see figure 1)
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