Doping is one of the most relevant paths to tune the functionality of
cuprates, it determines carrier density and the overall physical properties of
these impressive superconducting materials. We present an oxygen doping study
of YBa2βCu3βO7βΞ΄β (YBCO) thin films from underdoped to overdoped
state, correlating the measured charge carrier density, nHβ, the
hole doping, p, and the critical current density, Jcβ. Our results
show a continuous increase of Jcβ with charge carrier density,
reaching 90 MA/cm2 at 5 K for p-doping at the Quantum Critical Point
(QCP), linked to an increase of the superconducting condensation energy. The
ultra-high Jcβ achived corresponds to a third of the depairing
current, i.e. a value 60 % higher than ever reported in YBCO films. The
overdoped regime is characterized by a sudden increase of nHβ,
associated to the reconstruction of the Fermi-surface at the QCP. Overdoping
YBCO opens a promising route to extend the current carrying capabilities of
REBCO coated conductors for applications