Dispersion relation and spectral functions of the t-J model and the antiferromagnetic insulator Sr₂CuO₂Cl₂

We study the spectral functions of the single-hole t-J model with farther-than-nearest-neighbor and three-site hopping terms on a 32-site square lattice by exact diagonalization. We compare our results to the angle-resolved photoemission data of Sr₂CuO₂Cl₂, and find that this model closely mimics the experimental results except in the neighborhood of k = (π/2, 0). Further, we have determined that an energy-dependent broadening function is important in accounting for the incoherent contributions to the spectral functions.