Indirect Communication Between Non-Markovian Baths

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)].