Disappearance of Superconductivity Due to Vanishing Coupling in the Overdoped Cuprate Superconductors

In high-temperature cuprate superconductors, superconductivity is accompanied by a "plethora of orders" and phenomena that may compete, or cooperate with superconductivity, but which certainly complicate our understanding of origins of superconductivity. While prominent in the underdoped regime, these orders weaken or completely vanish with overdoping. Here, we approach the superconducting phase from the more conventional highly overdoped side. We present angle-resolved photoemission studies of Bi₂Sr₂CaCu₂O_8+δ single crystals cleaved and annealed in ozone to increase the doping all the way to the non-superconducting phase. We show that the mass renormalization in the antinodal region of the Fermi surface, associated with the structure in the quasiparticle self-energy, that possibly reflects the pairing interaction, monotonically weakens with increasing doping and completely disappears precisely where superconductivity disapears. This is the evidence that in the overdoped regime, superconductivity is determined by the coupling strength. A strong doping dependence and an abrupt disapearance above T_c eliminate the conventional phononic mechanism of the observed mass renormalization.