Quantum Criticality Due to Incipient Phase Separation in the Two-dimensional Hubbard Model

TL;DR

This paper studies the two-dimensional Hubbard model with next-nearest-neighbor hopping, revealing a quantum critical point linked to phase separation and the transition between Fermi liquid and pseudogap phases.

Contribution

It demonstrates the existence of a line of second-order critical points ending at a quantum critical point in the Hubbard model with next-nearest-neighbor hopping.

Findings

First-order phase separation transition confirmed.

Critical temperature T_ps approaches zero as t' approaches zero.

Quantum critical point separates Fermi liquid and pseudogap phases.

Abstract

We investigate the two-dimensional Hubbard model with next-nearest-neighbor hopping, t', using the dynamical cluster approximation. We confirm the existence of a first-order phase-separation transition terminating at a second-order critical point at filling n_c(t') and temperature T_ps(t'). We find that as t' approaches zero, T_ps(t') vanishes and n_c(t') approaches the filling associated with the quantum critical point separating the Fermi liquid from the pseudogap phase. We propose that the quantum critical point under the superconducting dome is the zero-temperature limit of the line of second-order critical points.