  The antiferromagnetic ground state of copper oxide Mott insulators is
achieved by localizing an electron at each copper atom in real space (r-space).
Removing a small fraction of these electrons (hole doping) transforms this
system into a superconducting fluid of delocalized Cooper pairs in momentum
space (k-space). During this transformation, two distinctive classes of
electronic excitations appear. At high energies, the enigmatic 'pseudogap'
excitations are found, whereas, at lower energies, Bogoliubov quasi-particles
-- the excitations resulting from the breaking of Cooper pairs -- should exist.
To explore this transformation, and to identify the two excitation types, we
have imaged the electronic structure of Bi2Sr2CaCu2O8+d in r-space and k-space
simultaneously. We find that although the low energy excitations are indeed
Bogoliubov quasi-particles, they occupy only a restricted region of k-space
that shrinks rapidly with diminishing hole density. Concomitantly, spectral
weight is transferred to higher energy r-space states that lack the
characteristics of excitations from delocalized Cooper pairs. Instead, these
states break translational and rotational symmetries locally at the atomic
scale in an energy independent fashion. We demonstrate that these unusual
r-space excitations are, in fact, the pseudogap states. Thus, as the Mott
insulating state is approached by decreasing the hole density, the delocalized
Cooper pairs vanish from k-space, to be replaced by locally translational- and
rotational-symmetry-breaking pseudogap states in r-space.
