Spatial structures and localization of vacuum entanglement in the linear harmonic chain

We study the structure of vacuum entanglement for two complimentary segments of a linear harmonic chain, applying the modewise decomposition of entangled Gaussian states discussed by Boteno and Reznik Phys. Rev. A 67, 052311 (2003). We find that the resulting entangled mode-shape hierarchy shows a distinctive layered structure with well-defined relations between the depth of the modes, their characteristic wavelength, and their entanglement contribution. We rederive in the strong coupling (diverging correlation length) regime, the logarithmic dependence of entanglement on the segment size predicted by conformal field theory for the boson universality class and discuss its relation with the mode structure. We conjecture that the persistence of vacuum entanglement between arbitrarily separated finite-size regions is connected with the localization of the highest-frequency innermost modes.