Coherence trapping and information backflow in dephasing qubits

We study the interplay between coherence trapping, information backflow and the form of the reservoir spectral density for dephasing qubits. We show that stationary coherence is maximized when the qubit undergoes non-Markovian dynamics, and we elucidate the different roles played by the low- and high-frequency parts of the environmental spectrum. We show that the low frequencies fully determine the presence or absence of information backflow while the high frequencies dictate the maximal amount of coherence trapping.