Abstract
The electron doping of undoped high-$T_c$ cuprates via the transfer of charge
from manganites (or other oxides) using heterostructure geometries is here
theoretically
discussed. This possibility is mainly addressed via a detailed analysis
of photoemission and diffusion voltage experiments, which locate the Fermi level
of manganites above the bottom of the upper Hubbard band of some cuprate parent
compounds. A diagram with the relative location of Fermi levels and gaps
for several oxides is presented. The procedure discussed here is generic,
allowing for
the qualitative prediction of the charge flow direction at several oxide interfaces.
The addition of electrons to antiferromagnetic Cu oxides
may lead to a
superconducting state at the interface with minimal quenched disorder.
%if the manganite used is not spin polarized.
Model calculations using static and dynamical mean-field theory, supplemented
by a Poisson equation formalism to address charge redistribution at the interface,
support this view. The magnetic state of the manganites could be antiferromagnetic
or ferromagnetic. The former is better to induce superconductivity than the latter,
since the spin-polarized charge transfer will
be detrimental to singlet superconductivity.
It is concluded that in spite
of the robust Hubbard gaps, the electron doping of undoped cuprates
at interfaces appears possible, and its realization may open an exciting
area of research in oxide heterostructures.
