Single-hole Green's functions in insulating copper oxides at nonzero temperature

We consider the single-hole dynamics in a modified t-J model at finite temperature. The modified model includes a next-nearest (t') and next-next-nearest (t " hopping. The model has been considered before in the zero temperature limit to explain angle-resolved photoemission measurements. We extend this consideration to the case of finite temperature where long-range antiferromagnetic order is destroyed, using the self-consistent Born approximation. The Dyson equation which relates the single-hole Green's functions for a fixed pseudospin and for fixed spin is derived. The Green's function with fixed pseudospin is infrared stable but the Green's function with fixed spin is close to an infrared divergency. We demonstrate how to renormalize this Green's function in order to assure numerical convergence. At nonzero temperature the quasiparticle peaks shift to lower energy and are broadened. The temperature broadening is, however, not enough to explain the widths of the experimental data, indicating that other degrees of freedom contribute to the quasiparticle damping.