Quantum State Tuning of Energy Transfer in a Correlated Environment

We investigate multichromophoric energy transfer allowing for bath-induced fluctuations at different sites to be correlated. As a prototype system, we consider a light-harvesting antenna surrounding a reaction center. We show that the interplay between quantum coherence and correlated fluctuations can generate a room-temperature transfer process featuring a marked dependence on the degree of symmetry and delocalization of the initial exciton state. Our work illustrates how these quantum features could support fine-tuning of energy transfer efficiencies in closely packed natural and artificial light-harvesting complexes

Coherent Energy Transfer under Incoherent Light Conditions

Recent two-dimensional electronic spectroscopy (2DES) experiments have reported evidence of coherent dynamics of electronic excitations in several light-harvesting antennae. However, 2DES uses ultrafast coherent laser pulses as an excitation source; therefore, there is a current debate on whether coherent excitation dynamics is present under natural sunlight – incoherent – illumination conditions. In this letter, we show that even if incoherent light excites an electronic state with no initial quantum superpositions among excitonic states, energy transfer can proceed quantum coherently if nonequilibrium dynamics of the phonon environment takes place. Such nonequilibrium behavior manifests itself in non-Markovian evolution of electronic excitations and is typical of many photosynthetic systems. We therefore argue that light-harvesting antennae have mechanisms that could support coherent evolution under incoherent illumination