Quantum Phase Transitions in 2D--dimensional paramagnetic half--filled Hubbard model

We investigate the quantum phase transitions in strongly correlated electronic systems at $T=0^{0}K$ by the example of the 2D Hubbard model. The model for numerical calculations were formalized in terms of the integral equations previously obtained for the half–filled paramagnetic Hubbard model by means of the variational derivatives technique and subsequent Legendre transformation. For principal results we submit in series the momentum distribution functions $n(k)$ which display distinct attributes for the incipient regimes: the pure doublon phase, the metal phase, Weyl semimetal phase, and Weyl excitonic insulator phase at the sequential increasing the onsite Coulomb interaction $U$.