Simulation of absorption spectra of molecular aggregates: a Hierarchy of Stochastic Pure States approach

TL;DR

This paper introduces a normalized Hierarchy of Pure States (HOPS) approach for simulating absorption spectra in large molecular aggregates, enabling more efficient and accurate spectroscopic calculations involving complex vibrational couplings.

Contribution

It develops a normalized dyadic equation for HOPS, allowing separate propagation of ket- and bra-states, facilitating adaptive methods for absorption and non-linear spectroscopy simulations.

Findings

Enables simulation of large aggregate absorption spectra with improved efficiency.

Provides a formalism for non-linear spectroscopy perturbative in electric field interactions.

Opens new avenues for applying stochastic pure state methods in complex spectroscopic calculations.

Abstract

The simulation of spectroscopic observables for molecular aggregates with strong and structured coupling of electronic excitation to vibrational degrees of freedom is an important but challenging task. The hierarchy of pure states (HOPS) provides a formally exact solution based on local, stochastic trajectories. Exploiting the localization of HOPS for the simulation of absorption spectra in large aggregares requires a formulation in terms of normalized trajectories. Here we provide a normalized dyadic equation where the ket- and bra-states are propagated in different electronic Hilbert spaces. This work opens the door to apply adaptive HOPS methods for the simulation of absorption spectra and also to a formulation for non-linear spectroscopy that is perturbative with respect to interactions with the electric field.