Underdoped cuprate phenomenology in the two-dimensional Hubbard model within the composite operator method

The two-dimensional Hubbard model is studied within the composite operator method (COM) with the self-energy computed in the self-consistent Born approximation (SCBA). The COM describes interacting electrons in terms of the new elementary excitations that appear in the system owing to strong correlations; residual interactions among these excitations are treated within the SCBA. On decreasing the doping (from the overdoped to underdoped region), anomalous features develop in the spectral function A(k,omega), the Fermi surface, the momentum distribution function n(k), the dispersion, and the density of states N(omega) in the intermediate-coupling regime (U=8) at low temperatures (T=0.01-0.02). At high doping (n=0.7), the system resembles an ordinary weakly interacting metal. At low doping (n=0.92), a pseudogap opens, hot and cold spots appear, and non-Fermi-liquid features develop. This behavior, together with the presence of kinks in the calculated electronic dispersion, is in agreement with angle-resolved photoemission spectroscopy data for high-T-c cuprates superconductors.