Signatures of spatially correlated noise and non-secular effects in two-dimensional electronic spectroscopy

TL;DR

This paper explores how correlated environmental noise and non-secular effects influence oscillatory signals in 2D electronic spectra of a model dimer, providing analytical insights and implications for interpreting spectral features.

Contribution

It offers a quantitative analytical framework for understanding non-secular effects and noise correlations in 2D spectra, linking spectral asymmetries to environmental fluctuation correlations.

Findings

Increased noise correlation extends oscillation lifetimes at specific spectral peaks.

Non-secular couplings induce oscillations at both cross- and diagonal-peaks.

Spectral asymmetry reveals the degree of environmental noise correlations.

Abstract

We investigate how correlated fluctuations affect oscillatory features in rephasing and non-rephasing two-dimensional (2D) electronic spectra of a model dimer system. Based on a beating map analysis, we show that non-secular environmental couplings induced by uncorrelated fluctuations lead to oscillations centered at both cross- and diagonal-peaks in rephasing spectra as well as in non-rephasing spectra. Using an analytical approach, we provide a quantitative description of the non-secular effects in terms of the Feynman diagrams and show that the environment-induced mixing of different inter-excitonic coherences leads to oscillations in the rephasing diagonal-peaks and non-rephasing cross-peaks. We demonstrate that as correlations in the noise increase, the lifetime of oscillatory 2D signals is enhanced at rephasing cross-peaks and non-rephasing diagonal-peaks, while the other non-secular oscillatory signals are suppressed. We discuss that the asymmetry of 2D lineshapes in the beating map provides information on the degree of correlations in environmental fluctuations. Finally we investigate how the oscillatory features in 2D spectra are affected by inhomogeneous broadening.