Breakdown of the Fermi-liquid regime in the 2D Hubbard model from a two-loop field-theoretical renormalization group approach

TL;DR

This study uses a two-loop field-theoretical renormalization group approach to analyze the 2D Hubbard model, revealing a non-Fermi liquid regime with a truncated Fermi surface that transitions into a correlated metal and eventually favors d-wave pairing.

Contribution

It introduces a two-loop RG analysis to evaluate momentum-dependent anomalous dimensions, uncovering a non-Fermi liquid phase in the 2D Hubbard model.

Findings

Identification of a non-Fermi liquid regime with a truncated Fermi surface

Transition from NFL to correlated metal with a large Fermi surface

Dominance of d-wave pairing susceptibility at low temperatures

Abstract

We analyze the particle-hole symmetric two-dimensional Hubbard model on a square lattice starting from weak-to-moderate couplings by means of the field-theoretical renormalization group (RG) approach up to two-loop order. This method is essential in order to evaluate the effect of the momentum-resolved anomalous dimension $\eta(\textbf{p})$ which arises in the normal phase of this model on the corresponding low-energy single-particle excitations. As a result, we find important indications pointing to the existence of a non-Fermi liquid (NFL) regime at temperature $T\to 0$ displaying a truncated Fermi surface (FS) for a doping range exactly in between the well-known antiferromagnetic insulating and the $d_{x^2-y^2}$-wave singlet superconducting phases. This NFL evolves as a function of doping into a correlated metal with a large FS before the $d_{x^2-y^2}$-wave pairing susceptibility finally produces the dominant instability in the low-energy limit.