Repurposing dephasing for long-lived coherence in two-dimensional electronic spectroscopy
Phys. Rev. A 114, 032401 – Published 1 September, 2026
DOI: https://doi.org/10.1103/w496-d4b8
Abstract
Long-lived waiting-time beatings in two-dimensional electronic spectroscopy remain puzzling in strongly dephasing regimes, where excitonic coherence is expected to decay rapidly. These oscillations are often attributed to environmental memory, typically modeled by resonance with a discrete mode. Here we show that they can instead arise within a Bloch-Redfield framework when bath memory, enhanced by low-frequency spectral weight, is carried across ultrafast pulse boundaries. The resulting three-pulse kernel retains nonsecular population-coherence transfer through the propagation of bath memory across pulse boundaries, generating cross-peak beatings without invoking resonant modes. Benchmarks against a reaction-coordinate master equation, spanning frequencies from small to well above the exciton scale, confirm the predicted low-frequency coherence-revival mechanism. The beatings thus arise from environmental displacements, which drive population-coherence transfer while damping coherence at comparable rates, thereby sustaining a finite coherence amplitude.
