Quantum Charge Migration in Light-Harvesting Chromophores *

Mounting experimental evidence suggests that the high efficiency of energy conversion in living beings relies on the quantum nature of charge transfer [1]. Attosecond laser technology allows us to study these ultrafast processes at the molecular level and at their natural time scale. Here, we present an ab-initio method to simulate the evolution of the correlated electronic state of a molecule under the action of arbitrarily polarized ultrashort light pulses in the presence of decoherence and apply it to organic molecules of biological relevance. The molecular excited electronic states are obtained from MCSCF calculations [2] while the effects of driving pulses and decoherence are taken into account by solving numerically the time-dependent Lindblad equation [4] for the density matrix of the system. The migration of charge is tracked using Becke’s charge-partitioning algorithm [5]. Finally, from the dipolar response of the light-dressed molecule, we reconstruct the observable susceptibility and relate it to specific charge migration modes predicted by theory. We demonstrate the potential of this method and show that decoherence favors a few modes, which can be controlled with light pulses to localize charge fluctuations on specific moieties.

 

[1] Y Kim et al., Quantum Rep., 3, 80 (2021)

 

[2] I Fdez. Galván, J. Chem. Th. Comput. 15, 5925 (2019) 

[3] F. Nathan, Phys. Rev. B, 102, 115109 (2020)

 

[4] H. Gharibnejad, Comput. Phys. Commun, 263,107889 (2021)