  Doping of strongly layered ionic oxides is an established paradigm for
creating novel electronic behavior. This is nowhere more apparent than in
superconductivity, where doping gives rise to high temperature
superconductivity in cuprates (hole-doped) and to surprisingly high Tc in HfNCl
(Tc=25.5K, electron-doped). First principles calculations of hole-doping of the
layered delafossite CuAlO2 reveal unexpectedly large doping-induced shifts in
spectral density, strongly in opposition to the rigid band picture that is
widely used as an accepted guideline. These spectral shifts, of similar origin
as the charge transfer used to produce negative electron affinity surfaces and
adjust Schottky barrier heights, drastically alter the character of the Fermi
level carriers, leading in this material to an O-Cu-O molecule-based carrier
(or polaron, at low doping) rather than a nearly pure-Cu hole as in a rigid
band picture. First principles linear response electron-phonon coupling (EPC)
calculations reveal, as a consequence, net weak EPC and no superconductivity
rather than the high Tc obtained previously using rigid band expectations.
These specifically two-dimensional dipole-layer driven spectral shifts provides
new insights into materials design in layered materials foe functionalities
besides superconductivity.
