title: Multiphonon transitions in the biomolecular energy transfer dynamics.
abstract: We show that the biomolecular exciton dynamics under the influence of slow polarization fluctuations in the solvent cannot be described by lowest order, one-phonon approaches which are perturbative in the system-bath coupling. Instead, nonperturbative multiphonon transitions induced by the slow bath yield significant contributions. This is shown by comparing results for the decoherence rate of the exciton dynamics of a resumed perturbation theory with numerically exact real-time path-integral data. The exact decoherence rate for realistically slow solvent environments is significantly modified by multiphonon processes even in the weak coupling regime, while a one-phonon description is satisfactory only for fast environmental noise. Slow environments inhibit bath modes that are resonant with the exciton dynamics, thereby suppressing one-phonon transitions and enhancing multiphonon processes, which are typically not captured by lowest order perturbative treatments, such as Redfield or Lindblad approaches, even in more refined variants.
authors.affiliation: Freiburg Institute for Advanced Studies (FRIAS), School of Soft Matter Research, Albert-Ludwigs-Universität Freiburg, Albertstrasse 19, 79104 Freiburg, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Nalbach
authors.forename: M
authors.initials: M
authors.lastname: Thorwart
mesh_terms: D004735:Energy Transfer; D011789:Quantum Theory; D014732:Vibration