Non-Markovianity in a dressed qubit with local dephasing

TL;DR

This paper investigates how a dressed qubit's coherence dynamics are influenced by non-Markovian effects arising from different bath spectral densities, revealing that memory effects depend on coupling strength and bath type.

Contribution

It introduces a perturbative approach using Lang-Firsov transformation and time-convolutionless master equation to analyze non-Markovianity in a dressed qubit system with various bath spectra.

Findings

Longer coherence times at large coupling values.

Non-monotonic decay patterns indicating non-Markovianity.

Pronounced memory effects in sub-Ohmic baths at small couplings.

Abstract

We study the dynamics of a dressed qubit implemented by a spinless fermion hopping between two lattice sites with each site strongly coupled to a bath of phonons. We employ Lang-Firsov transformation to make the problem tractable perturbatively. Applying time-convolutionless master equation within the polaron frame, we investigate decoherence dynamics of the dressed qubit within the singlet-triplet basis of the system for a wide range of bath spectral densities. It is shown that the coherence persists for longer time scales for large coupling values and shows non-monotonic behaviour reflecting the presence of non-Markovianity in the dynamics. Non-Markovianity, characterized by coherence revivals and non-monotonic decay patterns, emerges distinctly depending on the bath spectrum and coupling strengths. Systems coupled to sub-Ohmic baths, whether both or in combination with another type, display pronounced memory effects at relatively small values of couplings. In contrast, combinations involving Ohmic and super-Ohmic baths exhibit noticeable non-Markovianity only at higher couplings.