Remnant Fermi surface in a pseudogap regime of the two-dimensional Hubbard model at finite temperature

TL;DR

This study investigates the effects of spin fluctuations on the Fermi surface in the two-dimensional Hubbard model at finite temperature, revealing the destruction of the Fermi surface near the pseudogap regime using multiple theoretical approaches.

Contribution

It introduces a comparative analysis of the Fermi surface behavior near the pseudogap regime using second order perturbation, PT, and TPSC approaches at finite temperature.

Findings

Fermi surface is destroyed near the pseudogap regime due to spin fluctuations.

The top of the effective valence band is around (π/2,π/2), consistent with previous studies.

A crossover from Fermi-liquid to pseudogap regime is observed in spectral functions.

Abstract

A precursor effect on the Fermi surface in the two-dimensional Hubbard model at finite temperatures near the antiferromagnetic instability is studied using three different itinerant approaches: the second order perturbation theory, the paramagnon theory (PT), and the two-particle self-consistent (TPSC) approach. In general, at finite temperature, the Fermi surface of the interacting electron systems is not sharply defined due to the broadening effects of the self-energy. In order to take account of those effects we consider the single-particle spectral function $A({\bf k},0)$ at the Fermi level, to describe the counterpart of the Fermi surface at T=0. We find that the Fermi surface is destroyed close to the pseudogap regime due to the spin-fluctuation effects in both PT and TPSC approaches. Moreover, the top of the effective valence band is located around ${\bf k}=(\pi/2,\pi/2)$ in agreement with earlier investigations on the single-hole motion in the antiferromagnetic background. A crossover behavior from the Fermi-liquid regime to the pseudogap regime is observed in the electron concentration dependence of the spectral function and the self-energy.