Systematics of the Photoemission Spectral Function of Cuprates: Insulators and Hole- and Electron-Doped Superconductors

Angle-resolved photoemission studies on ${\mathrm{Sr}}_2{\mathrm{CuO}}_2{\mathrm{Cl}}_2$ at a temperature below its Néel temperature reveal detailed momentum dependent line shape changes as a function of wave vector. While a sharp quasiparticlelike peak is observed near ( $\pi /2,\pi /2$), broad peaks are observed near ( $\pi ,0\mathrm{}$). Additional second and third neighbor hopping terms must be added to the $t-J$ Hamiltonian to account for both the dispersion and the line shape. It is found that this Hamiltonian can be used to explain the measured momentum dependent spectral function for hole-doped materials, both underdoped and overdoped, as well as electron-doped materials.