Quantum master equations and steady states for the ultrastrong-coupling limit and the strong-decoherence limit

In the framework of the theory of open quantum systems, we derive quantum master equations for the ultrastrong system-bath coupling regime and, more generally, the strong-decoherence regime. In this regime, the strong decoherence is complemented by slow relaxation processes. We use a generalization of the Forster and modified Redfield perturbation theories known in the theory of excitation-energy transfer. Also, we show that the mean-force Gibbs state in the corresponding limits is stationary for the derived master equations.

Automated summary

In this paper, we investigate the ultrastrong system-bath coupling regime and the strong-decoherence regime in the framework of the theory of open quantum systems. By deriving quantum master equations, we find that strong decoherence is complemented by slow relaxation processes in these regimes.