No well-defined remnant Fermi surface in ${\mathrm{Sr}}_2{\mathrm{CuO}}_2{\mathrm{Cl}}_2$

In angle-resolved photoelectron spectra of the antiferromagnetic insulators ${\mathrm{Ca}}_2{\mathrm{CuO}}_2{\mathrm{Cl}}_2$ and ${\mathrm{Sr}}_2{\mathrm{CuO}}_2{\mathrm{Cl}}_2,$ a sharp drop of the spectral intensity of the lowest-lying band is observed along a line in k space equivalent to the Fermi surface of the optimally doped high-temperature superconductors. This was interpreted as a signature of the existence of a remnant Fermi surface in the insulating phase of the high-temperature superconductors. In this paper it is shown that the drop of the spectral intensity is not related to the spectral function but is a consequence of the electron-photon matrix element.