Stabilizing quantum coherence against pure dephasing in the presence of quantum feedback at finite temperature

A general formalism to describe the dynamics of quantum emitters in structured reservoirs is introduced. As an application, we investigate the optical coherence of an atom-like emitter diagonally coupled via a link-boson to a structured bosonic reservoir and obtain unconventional dephasing dynamics due to non-Markovian quantum feedback for different temperatures. For a two-level emitter embedded in a phonon cavity preservation of finite coherence is predicted up to room temperature.