The calculation of the Fermi surface with complex topology from norm-conserving cluster perturbation theory for doping dependent electronic structure of the Hubbard model

In present paper the results of recently developed norm-conserving cluster perturbation theory (NC–CPT) for doping dependent electronic structure of the Hubbard model are reported. We have found that the momentum distribution of the spectral weight strongly depends on the broadening value $\delta$. At the $\delta = 0.1t$ we reproduce the angleṛesolved photoemission spectroscopy (ARPES) data, while at $\delta = 0.01t$ we obtain two quantum phase transitions (QPT).