  The superconductivity in high temperature superconductors ordinarily arises
when doped with hetero-valent ions that introduce charge carriers. However, in
ferropnictides, "iso-valent" doping, which is generally believed not to
introduce charge carriers, can induce superconductivity as well. Moreover,
unlike other ferropnictides, the superconducting gap in BaFe2(As1-xPx)2 has
been found to contain nodal lines. The exact nature of the "iso-valent" doping
and nodal gap here are key open issues in building a comprehensive picture of
the iron-based high temperature superconductors. With angle-resolved
photoemission spectroscopy (ARPES), we found that the phosphor substitution in
BaFe2(As1-xPx)2 induces sizable amount of holes into the hole Fermi surfaces,
while the dxy-originated band is relatively intact. This overturns the previous
common belief of "iso-valent" doping, explains why the phase diagram of
BaFe2(As1-xPx)2 is similar to those of the holedoped compounds, and rules out
theories that explain the nodal gap based on vanishing dxy hole pocket.
