Photoemission Studies of the Pseudogap Regime in the High Tc Cuprate Phase Diagram

By examining thermally excited states above the Fermi level in angle resolved photoemission spectroscopy, we show that the disconnected Fermi arcs observed in the pseudogap state of the cuprate phase diagram are actually components of fully enclosed hole pockets. The spectral weight of these pockets is vanishingly small at the Luttinger surface, coincident with the antiferromagnetic zone-boundary formed by the underlying spin lattice, creating the illusion of the Fermi arcs. The area of the pockets as measured in this study is consistent with the doping level, and hence the carrier density, of the samples measured. Furthermore, the shape and area of the pockets is well reproduced by phenomenological models of the pseudogap phase that reflect its proximity to a Mott insulator.