Impact of solvent on state-to-state population transport in multistate systems using coherences

Abstract

We present an approach of analyzing the transport of a quantum particle in a non-trivially connected extended system interacting with a dissipative medium. There are broadly two different aspects of the problem that affect the route taken by the transport process. First is obviously the couplings between the various sites, which translates into the intrinsic "strength" of a channel. Apart from the inter-site couplings, the solvents affecting the energies of the sites, and their relative coupling strengths and time-scales form the second factor. This impact of the such dissipative media is significantly more difficult to analyze. The Channel-Dependent Population Transfer (CDPT) method of analyzing the transport allows us to account for both the effects in a rigorous manner. We demonstrate the richness hidden behind the transport even for relatively simple systems -the effect of the local dissipative media is highly non-trivial and can mask the simplicity of the effect of the relative magnitude of the inter-site couplings. This opens up possibilities in terms of detailed study of the impact of factors on the nature of dynamics, especially possibilities of design of novel systems with an eye towards quantum control.

Impact of Spatial Inhomogeneity on Excitation Energy Transport in the Fenna-Matthews-Olson Complex

“…The usual practice is to focus the numerical studies on the evolution of the population in the excited states of each of the chromophores. Here, we additionally use the recently developed coherencebased analytic techniques [43][44][45][46] to unravel the pathways that the excitation takes and the impact of the vibrational modes. Baker and Habershon [47] have explored these pathways in FMO using the Lindblad master equation.…”

“…More recently, Dani and Makri have shown that the time-derivative of the on-site populations is related to linear combinations of the off-diagonal terms of the reduced density matrix [44], and visualized the coherences in forms of maps that encode information about the dynamics of the system [45]. We extended these ideas to partition the time-dependent population change on a site in terms of transport along different state-to-state channels, which is useful for understanding the instantaneous population transfer in these systems with complex interconnects [46]. To explore the overall importance of the different pathways using this coherence-based analysis, we use a modified version of the integrated flux approach [43] and define a time-averaged state-to-state population transfer:…”

“…There is a limit to the amount of information that can be extracted from the direct population dynamics. We have used the recently introduced ideas of relating the coherence to the population transport [44][45][46] to explore the routes of transfer that the molecular excitation takes. Given the very complex interactions between these chromophores, it is not trivial to use an exact numerical computation to attribute the excitation transport to the different directed path-ways that exist.…”