Comparison of 32-site exact diagonalization results and ARPES spectral functions for the antiferromagnetic insulator Sr2CuO2Cl2

We explore the success of various versions of the one-band t-J model in explaining the full spectral functions found in angle-resolved photoemission spectra for the prototypical, quasi-two-dimensional, tetragonal, antiferromagnetic insulator Sr2CuO2Cl2. After presenting arguments justifying our extraction of A(k,omega) from the experimental data, we rely on exact-diagonalization results from studies of a square 32-site lattice, the largest cluster for which such information is presently available, to perform this comparison. Our work leads us to believe that (i) a one-band model that includes hopping out to third-nearest neighbors, as well three-site, spin-dependent hopping, can indeed explain not only the dispersion relation, but also the quasiparticle lifetimes-only in the neighborhood of k=(pi/2,0) do we find disagreement; (ii) an energy-dependent broadening function, Gamma(E)=Gamma(0)+AE, is important in accounting for the incoherent contributions to the spectral functions.