Forster resonance energy transfer, absorption and emission spectra in multichromophoric systems: III. Exact stochastic path integral evaluation

TL;DR

This paper introduces a numerically exact stochastic path integral method for calculating absorption and emission spectra in large multichromophoric quantum systems, enabling accurate energy transfer rate computations across diverse conditions.

Contribution

It presents a new stochastic path integral approach that efficiently and accurately computes spectra and energy transfer rates in complex quantum systems, surpassing previous perturbative methods.

Findings

Rapid convergence of the stochastic method for large systems

Accurate spectra and transfer rates across broad parameter ranges

Hybrid cumulant expansion outperforms other perturbative methods

Abstract

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators one can also immediately compute energy transfer rates using the multi-chromophoric Forster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion is the only perturbative method capable of generating uniformly reliable energy transfer rates and spectra across a broad range of system parameters.