Continuous doping of a cuprate surface: Insights from <i>in situ</i> angle-resolved photoemission

Abstract

We report a technique of a continuously doped surface of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+x}$ through ozone/vacuum annealing and a systematic measurement over the nearly whole superconducting dome on the same sample surface by in situ angle-resolved photoemission spectroscopy. We find that the quasiparticle weight on the antinode is proportional to the doped carrier concentration $x$ within the entire superconducting dome, while the nodal quasiparticle weight changes more mildly. More significantly, we discover that a $d$-wave pairing energy gap extracted from the nodal region scales well with the onset temperature of the Nernst signal. These findings suggest that the emergence of superconducting pairing is concomitant with the onset of free vortices.