  We address the non-Markovian entanglement dynamics for bimodal continuous
variable quantum systems interacting with two independent structured
reservoirs. We derive an analytical expression for the entanglement of
formation without performing the Markov and the secular approximations. We
observe a variety of qualitative features such as entanglement sudden death,
dynamical generation, and protection for two types of Lorentzian spectral
densities, assuming the two modes initially excited in a twin-beam state. Our
quantitative analysis shows that these cases with different reservoir spectrum,
the environmental temperature and the initial amount of entanglement differ
significantly in these qualitative features.
