Indirect Communication Between Non-Markovian Baths

TL;DR

This paper introduces a novel two-bath model combining an overdamped Lorentz-Drude environment with an undamped oscillator, revealing bath-mediated information transfer and non-Markovian dynamics, with implications for spectral analysis.

Contribution

It develops the LDUO-HEOM framework for a new two-bath system, demonstrating bath-mediated information transfer without direct bath coupling.

Findings

Information transfer occurs between baths without direct coupling.

The model reproduces qualitative features of 2D electronic spectra.

Eliminates superfluous damping from finite spectral width.

Abstract

In this work we develop a model for an undamped vibration in the presence of an overdamped bath. This two-bath model involves a new derivation of the hierarchical equations of motion (HEOM) for an overdamped Lorentz-Drude (LD) environment that is summed together with an undamped oscillator (UO) bath, termed LDUO-HEOM. We show that information transfer occurs between the two baths, even in the absence of a direct coupling between the baths. This bath-system-bath, mediated information transfer leads to intricate non-Markovian dynamics. The model is analysed using expectation values of the bath coordinates and generates 2D electronic spectra that are in qualitative agreement with single-bath models. Furthermore, the model eliminates the additional superfluous damping introduced by the finite spectral width of the underdamped bath in our previous two-bath underdamped-overdamped, `bath vibration model' [J. Chem. Phys. 156, 084103 (2022)].