  The charge dynamics in weakly hole doped high temperature superconductors is
studied in terms of the accurate numerical solution to a model of a single hole
interacting with a quantum lattice in an antiferromagnetic background, and
accurate far-infrared ellipsometry measurements. The experimentally observed
two electronic bands in the infrared spectrum can be identified in terms of the
interplay between the electron correlation and electron-phonon interaction
resolving the long standing mystery of the mid-infrared band.
