Compressibility of the Two-Dimensional infinite-U Hubbard Model

TL;DR

This paper investigates the compressibility and phase transition in the infinite-U Hubbard model, revealing a divergence at a critical doping and exploring implications for phase separation and superconductivity.

Contribution

It provides a systematic large-N expansion analysis of quasiparticle interactions and identifies a critical doping where compressibility diverges, indicating a phase transition.

Findings

Compressibility diverges at doping δ_c≈0.07.

Quasiparticle weight and mass are renormalized.

Connection to phase separation and superconductivity is discussed.

Abstract

We study the interactions between the coherent quasiparticles and the incoherent Mott-Hubbard excitations and their effects on the low energy properties in the $U=\infty$ Hubbard model. Within the framework of a systematic large-N expansion, these effects first occur in the next to leading order in 1/N. We calculate the scattering phase shift and the free energy, and determine the quasiparticle weight Z, mass renormalization, and the compressibility. It is found that the compressibility is strongly renormalized and diverges at a critical doping $\delta_c=0.07\pm0.01$. We discuss the nature of this zero-temperature phase transition and its connection to phase separation and superconductivity.