Coherent Exciton Dynamics in the Presence of Underdamped Vibrations.
Recent ultrafast optical experiments show that excitons in large biological light-harvesting complexes are coupled to molecular vibration modes. These high-frequency vibrations will not only affect the optical response, but also drive the exciton transport. Here, using a model dimer system, the frequency of the underdamped vibration is shown to have a strong effect on the exciton dynamics such that quantum coherent oscillations in the system can be present even in the case of strong noise. Two mechanisms are identified to be responsible for the enhanced transport efficiency: critical damping due to the tunable effective strength of the coupling to the bath, and resonance coupling where the vibrational frequency coincides with the energy gap in the system. The interplay of these two mechanisms determines parameters responsible for the most efficient transport, and these optimal control parameters are comparable to those in realistic light-harvesting complexes. Interestingly, oscillations in the excitonic coherence at resonance are suppressed in comparison to the case of an off-resonant vibration.
†Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
Arend G
AG
Dijkstra
‡Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602, Singapore.
Chen
C
Wang
†Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.|‡Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602, Singapore.
Jianshu
J
Cao
§Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|∥Department of Chemistry, University of California, Berkeley, California 94720, United States.
Graham R
GR
Fleming
D004735:Energy Transfer; D008958:Models, Molecular; D014732:Vibration
chlorosome; excitation energy transfer; exciton diffusion; exciton-vibration coupling; green sulfur bacteria; light-harvesting antenna system; non-Markovian effects