The dependence of exciton transport efficiency on spatial patterns of correlation within the spectral bath

Abstract

Spatial correlations in spectral bath motions have been proposed to explain long-lived coherence in exciton transport. Systems of interest, ranging from photosynthetic complexes to organic photovoltaics, contain inhomogeneous environments. We consider the possibility that the degree of spatial correlation varies throughout an exciton transport system. We model exciton transport in the Fenna-Matthews-Olson complex (FMO), a photosynthetic light-harvesting complex. Although it remains unclear whether significant spatial correlations exist in FMO, its very high exciton transport efficiency makes it an interesting case for studies of exciton transport. We also simulate a highly symmetric ten-site model system. We use an extension of the environment-assisted quantum transport model to simulate transport, allowing the spatial correlation function to vary throughout the system. We demonstrate both via analysis and via simulation that exciton transport efficiency is most sensitive to changes in correlation between the site coupled to the trap and its neighboring sites. This asymmetry in sensitivity is highly robust and appears irrespective of changes in parameters such as transition dipole orientations and initial conditions. Our results suggest that in the design of exciton transport

Transport of quantum excitations coupled to spatially extended nonlinear many-body systems

“…The first remarkable result is that nonlinear correlations in the lattice dynamics boost the efficiency in the Zeno-effect region (see diamonds versus squares in figure 9). This finding, although for somewhat different physical reasons, is in line with recent results where the importance of spatial correlations was demonstrated for transport in a PD-like model [83]. Furthermore, we note that such a behavior is consistent with the different scaling exponents of the diffusion constant D discussed in section 3.…”

“…Along the lines of previous studies, such as [20,82] and [83], we use equations (16) to investigate the competition between the two mechanisms of exciton destruction, namely generic recombination (γ r ) and exit through a specific channel (Γ). The whole idea is that an efficient transport is maximally effective in channeling the exciton rapidly through the specified exit site against the generic degradation due to recombination.…”

Efficient quantum transport in a multi-site system combining classical noise and quantum baths

“…Here, n=3 indicates the trap site and we have chosen tu=7 ps following similar arguments as in [17] . The trapping rate κ in equation (7) is chosen to have a relatively low value, 0.5 ps −1 , to be reasonably distant from the localization limit [48].…”

Focus on quantum efficiency

“…Given our much improved understanding of multicomponent, disordered, highly structured, open quantum systems, the present 'focus on' collection brings together cutting-edge research on theoretical and experimental aspects of quantum transport in truly complex systems as defined by, e.g., the macromolecular functional complexes at the heart of photosynthesis [3,6,12,14,16], or semiconductor (light-emitting) diodes [5,7]. All these examples involve transport of quantum particles or excitations as a crucial ingredient determining the efficiency of the respective system or device.…”

“…The mechanisms by which dissipative dynamics generates entanglement may furthermore lead to a better scaling of quantum metrology error with system size [4]. Last but not least, our 'focus on' collection also contains new results on the modeling of non-Markovian [11] or site-correlated [12] baths, which provide an additional degree of freedom for the optimisation of transport efficiencies.…”