Canonically consistent quantum master equation for proton-transfer reactions

TL;DR

This paper introduces the CCQME method for accurately modeling proton transfer reactions in molecules, demonstrating its effectiveness over traditional approaches by benchmarking against exact HEOM results.

Contribution

The paper presents the CCQME as a canonically consistent quantum master equation that improves upon Redfield theory for system-bath dynamics in proton transfer.

Findings

CCQME remains accurate at intermediate coupling strengths.

Redfield theory deviates from HEOM with increasing coupling.

Benchmarking confirms CCQME's reliability over Redfield in specific regimes.

Abstract

The canonically consistent quantum master equation (CCQME) method to treat system-bath dynamics is used to describe intramolecular proton transfer in the thioacetylacetone molecule (TAA, C$_4$H$_6$OS), modeled as an $N$-level quantum system coupled to a solvent. The solvent is represented as a harmonic bath (a continuum of oscillators) characterized by an Ohmic-Drude spectral density. We benchmark CCQME against numerically exact hierarchical equations of motion (HEOM) theory and compare to Redfield theory. Our results reveal that Redfield dynamics deviates increasingly from the HEOM reference as the system-bath coupling strength grows. In contrast, the recently proposed CCQME remains consistent with HEOM at intermediate coupling.