# Fluctuation diagnostics of the finite temperature quasi-antiferromagnetic regime of the 2D Hubbard model

## TL;DR

This study investigates the crossover from Fermi-liquid to non-Fermi-liquid behavior in the 2D Hubbard model at finite temperatures, highlighting the role of spin fluctuations and their impact on electronic properties.

## Contribution

The paper introduces fluctuation diagnostics within the dual fermion framework to analyze the self energy contributions, revealing the dominant role of $(\pi,\pi)$ spin fluctuations in non-Fermi-liquid behavior.

## Key findings

- Sharp $(\pi,\pi)$ spin fluctuations drive non-Fermi-liquid characteristics.
- Bosonic frequency contributions show complex dependence on frequency.
- Non-Fermi-liquid tendencies are similar for electron and hole doping.

## Abstract

We study the finite temperature Fermi-liquid to non-Fermi-liquid crossover in the 2D Hubbard model for a range of dopings using the self-consistent ladder dual fermion method. We consider relatively high temperatures where we identify a suppression of the density of states near the Fermi level caused by a quasi-antiferromagnetic behaviour that is itself characterized by a long, but finite, correlation length scale. We perform fluctuation diagnostics to decompose the single-particle self energy into scattering $q$-vector and bosonic frequency contributions. Within this framework we find that the key contributions to the single-particle self energy that give non-Fermi-liquid character, even at weak coupling, are caused by relatively sharp $q=(\pi,\pi)$ spin fluctuations, while the decomposition in the bosonic frequency channel shows a complicated dependence on the relative strengths of zero, positive and negative frequency contributions. Finally, variation in density suggests that the tendency towards non-Fermi-liquid behavior is not substantially different for electron or hole doped systems.