Person:
Eisfeld, Alexander

Profile Picture

Email Address

AA Acceptance Date

Birth Date

Research Projects

Organizational Units

Job Title

Last Name

Eisfeld

First Name

Alexander

Name

Eisfeld, Alexander
Author's Publications: search.filters.isAuthorOfPublication.5abbbaf2-a039-4965-90d3-8b84d7d6b2f7

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    On the Alternatives for Bath Correlators and Spectral Densities from Mixed Quantum-Classical Simulations
    (American Institute of Physics, 2012) Valleau, Stephanie; Eisfeld, Alexander; Aspuru-Guzik, Alan
    We investigate on the procedure of extracting a “spectral density” from mixed QM/MM calculations and employing it in open quantum systems models. In particular, we study the connection between the energy gap correlation function extracted from ground state QM/MM and the bath spectral density used as input in open quantum system approaches. We introduce a simple model which can give intuition on when the ground state QM/MM propagation will give the correct energy gap. We also discuss the role of higher order correlators of the energy-gap fluctuations which can provide useful information on the bath. Further, various semiclassical corrections to the spectral density, are applied and investigated. Finally, we apply our considerations to the photosynthetic Fenna-Matthews-Olson complex. For this system, our results suggest the use of the Harmonic prefactor for the spectral density rather than the Standard one, which was employed in the simulations of the system carried out to date.
  • Thumbnail Image
    Publication
    Photonics meets excitonics: natural and artificial molecular aggregates
    (Walter de Gruyter GmbH, 2013) Saikin, Semion K.; Eisfeld, Alexander; Valleau, Stephanie; Aspuru-Guzik, Alan
    Organic molecules store the energy of absorbed light in the form of charge-neutral molecular excitations -- Frenkel excitons. Usually, in amorphous organic materials, excitons are viewed as quasiparticles, localized on single molecules, which diffuse randomly through the structure. However, the picture of incoherent hopping is not applicable to some classes of molecular aggregates -- assemblies of molecules that have strong near field interaction between electronic excitations in the individual subunits. Molecular aggregates can be found in nature, in photosynthetic complexes of plants and bacteria, and they can also be produced artificially in various forms including quasi-one dimensional chains, two-dimensional films, tubes, etc. In these structures light is absorbed collectively by many molecules and the following dynamics of molecular excitation possesses coherent properties. This energy transfer mechanism, mediated by the coherent exciton dynamics, resembles the propagation of electromagnetic waves through a structured medium on the nanometer scale. The absorbed energy can be transferred resonantly over distances of hundreds of nanometers before exciton relaxation occurs. Furthermore, the spatial and energetic landscape of molecular aggregates can enable the funneling of the exciton energy to a small number of molecules either within or outside the aggregate. In this review we establish a bridge between the fields of photonics and excitonics by describing the present understanding of exciton dynamics in molecular aggregates.
  • Thumbnail Image
    Publication
    Absence of Quantum Oscillations and Dependence on Site Energies in Electronic Excitation Transfer in the Fenna–Matthews–Olson Trimer
    (American Chemical Society, 2011) Ritschel, Gerhard; Roden, Jan; Strunz, Walter T.; Aspuru-Guzik, Alan; Eisfeld, Alexander
    Energy transfer in the photosynthetic Fenna–Matthews–Olson (FMO) complex of green sulfur bacteria is studied numerically taking all three subunits (monomers) of the FMO trimer and the recently found eighth bacteriochlorophyll (BChl) molecule into account. The coupling to the non-Markovian environment is treated with a master equation derived from non-Markovian quantum state diffusion. When the excited-state dynamics is initialized at site eight, which is believed to play an important role in receiving excitation from the main light harvesting antenna, we see a slow exponential-like decay of the excitation. This is in contrast to the oscillations and a relatively fast transfer that usually occurs when initialization at sites 1 or 6 is considered. We show that different sets of electronic transition energies can lead to large differences in the transfer dynamics and may cause additional suppression or enhancement of oscillations.