Matrix-product-state-based calculations of exciton-phonon dynamics for light-harvesting complexes

Excitonic systems with one to a few dozen sites are an important topic in contexts such as quantum optics, molecular spectroscopy or the dynamics of light-harvesting complexes. However, the dynamics are often strongly influenced by coupling to the external or internal vibrational modes, which presents a computationally much more challenging problem. We investigate the dynamics of excitonic oligomers with such non-perturbative coupling to a quantum bath using a symmetry-adapted state-of-the-art matrix-product-state (MPS) code[1] which has not been previously applied to this type of system. Using this accurate, unbiased method, we focus on studying spreading, coherence and entanglement behavior. The insights gained from these analyses help us better understand exciton dynamics in photosynthesis, e.g. in the purple bacteria light-harvesting complex LH2, which exhibits efficient energy transfer and a notable symmetric structure. [2]

1: Time-evolution methods for matrix-product states; S. Paeckel, T. Köhler et al.; arXiv:1901.05824 [cond-mat.str-el]
2: Optimal fold symmetry of LH2 rings; L. Cleary, H. Chen et al.; PNAS 110 (21), 8537-8542 (May 2013); DOI: 10.1073/pnas.1218270110