Simulating optical linear absorption for mesoscale molecular aggregates: an adaptive hierarchy of pure states approach

TL;DR

This paper introduces DadHOPS, a novel computational method combining adaptive and dyadic HOPS techniques to efficiently simulate linear absorption spectra of large molecular aggregates, including static disorder effects.

Contribution

The paper develops DadHOPS, an innovative approach that achieves size-invariant scaling for large aggregates and incorporates static disorder through an initial state decomposition.

Findings

DadHOPS achieves size-invariant computational scaling for large aggregates.

The method effectively includes static disorder in spectral calculations.

Demonstrated on photosystem I and artificial molecular aggregates.

Abstract

In this paper, we present a new method for calculating linear absorption spectra for large molecular aggregates, called dyadic adaptive HOPS (DadHOPS). This method combines the adaptive HOPS (adHOPS) framework, which uses locality to improve computational scaling, with the dyadic HOPS method previously developed to calculate linear and non-linear spectroscopic signals. To construct a local representation of dyadic HOPS, we introduce an initial state decomposition which reconstructs the linear absorption spectra from a sum over locally excited initial conditions. We demonstrate the sum over initial conditions can be efficiently Monte Carlo sampled, that the corresponding calculations achieve size-invariant (i.e. $\mathcal{O}(1)$) scaling for sufficiently large aggregates, and that it allows for the trivial inclusion of static disorder in the Hamiltonian. We present calculations on the photosystem I core complex to explore the behavior of the initial state decomposition in complex molecular aggregates, and proof-of-concept DadHOPS calculations on an artificial molecular aggregate inspired by perylene bis-imide.