Pseudogap at hot spots in the two-dimensional Hubbard model at weak coupling

TL;DR

This paper investigates how weak interactions in the two-dimensional Hubbard model cause pseudogap features near hot spots, revealing complex self-energy effects and spectral function modifications through functional renormalization group analysis.

Contribution

It introduces a detailed analysis of pseudogap formation at hot spots in the weakly interacting 2D Hubbard model using the Wick-ordered functional renormalization group approach.

Findings

Enhanced interactions at hot spots lead to a pseudogap-like double-peak in spectral functions.

Self-energy effects beyond simple quasiparticle damping are significant near instabilities.

A pronounced low-energy peak in the imaginary part of the self energy is observed.

Abstract

We analyze the interaction-induced renormalization of single-particle excitations in the two-dimensional Hubbard model at weak coupling using the Wick-ordered version of the functional renormalization group. The self energy is computed for real frequencies by integrating a flow equation with renormalized two-particle interactions. In the vicinity of hot spots, that is points where the Fermi surface intersects the umklapp surface, self energy effects beyond the usual quasi-particle renormalizations and damping occur near instabilities of the normal, metallic phase. Strongly enhanced renormalized interactions between particles at different hot spots generate a pronounced low-energy peak in the imaginary part of the self energy, leading to a pseudogap-like double-peak structure in the spectral function for single-particle excitations.