Phonon-Induced Decoherence and Non-Markovian Dynamics in Strongly Coupled Quantum Dot–Microcavity Systems: A Non-Perturbative Variational Polaron Investigation

Abstract

The strong coupling of a single semiconductor quantum dot (QD) exciton to an optical microcavity mode forms the backbone of several quantum photonic technologies. However, the deformation-potential coupling of the exciton to longitudinal acoustic (LA) phonons in the host crystal introduces decoherence that fundamentally limits device performance. This article presents a thorough theoretical study of phonon-induced decoherence and non-Markovian dynamics in a strongly coupled single QD–microcavity system based on a non-perturbative variational polaron transformation. The total Hamiltonian—comprising the Jaynes–Cummings interaction and the independent boson model for the LA phonon bath—is formulated, and a variational polaron transformation with an optimized displacement parameter  is used to dress the excitonic state with a phonon cloud in a non-perturbative manner. The resulting variational master equation is solved to compute vacuum Rabi oscillation visibility, polariton linewidth, phonon sideband weight, and non-Markovian coherence dynamics for InAs/GaAs, GaAs/AlGaAs, and InGaAs/GaAs material platforms. At  K with   eV, the variational approach predicts a Rabi visibility  and a phonon sideband weight of 11.6%. Non-Markovian effects quantified by the Breuer–Laine–Piilo (BLP) measure reveal coherence revival phenomena driven by phonon information backflow, with InGaAs/GaAs showing the strongest non-Markovianity ( ). Comparisons with weak-coupling, full polaron, and numerically exact path-integral methods confirm the superior accuracy of the variational approach across all coupling regimes and temperatures.

DOI: https://doi-ds.org/doilink/04.2026-81688871