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

TL;DR

This paper explores quantum phase transitions in the 2D paramagnetic Hubbard model at zero temperature, identifying distinct electronic phases as the Coulomb interaction varies, using integral equation methods.

Contribution

It introduces a formalized numerical approach based on integral equations and Legendre transformation to analyze phase transitions in the 2D Hubbard model.

Findings

Identification of momentum distribution functions for different phases

Observation of transitions from doublon to metal to Weyl phases

Characterization of Weyl excitonic insulator phase

Abstract

We investigate the quantum phase transitions in strongly correlated electronic systems at $T=0^0K$ 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 $U$.