Momentum-dependent relaxation rate and pseudogap in doped magnetic insulators

The spectral functions and corresponding self-energies are calculated within the planar t-t(')-J model as relevant to hole-doped cuprates using the exact diagonalization method at finite temperatures, combined with the averaging over twisted boundary conditions. Results show truncated Fermi surface at low doping and t(')< 0 in the antinodal region, while the self-energy reveals weakly k- and doping-dependent anomalous relaxation rate parallel to Sigma(')(k,omega)parallel to similar to a+b parallel to omega parallel to for omega < 0, consistent with recent angle-resolved photoemission spectroscopy results, and a pseudogap-generating component. The latter is well pronounced at low doping and strongly depends on k and t(').