title: Coherent Energy Transfer under Incoherent Light Conditions.
abstract: 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.
authors: †Lash Miller Chemical Laboratories, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, 80 St. George St., Toronto, Ontario, M5S 3H6, Canada.
authors: Francesca
authors: F
authors: Fassioli
authors: ‡Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors: Alexandra
authors: A
authors: Olaya-Castro
authors: †Lash Miller Chemical Laboratories, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, 80 St. George St., Toronto, Ontario, M5S 3H6, Canada.
authors: Gregory D
authors: GD
authors: Scholes
keywords: incoherent excitation; light-harvesting; non-Markovian dynamics; quantum coherence; resonant energy transfer