Superconducting order parameter in heavily overdoped $B{i}_{2}S{r}_{2}CaC{u}_2{O}_{8+\delta }$: a global quantitative analysis

A systematic analysis of the complex lineshape at $(\pi ,0)$ of heavily overdoped Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ is presented. We show that a coherent component in the quasi-particle excitation is correlated with the superfluid density throughout the entire doping range and suggest it is a direct measure of the order parameter of high temperature superconductors.