Spin-fermion model with overlapping hot spots and charge modulation in cuprates

TL;DR

This paper investigates particle-hole instabilities in cuprates using an extended spin-fermion model, revealing a dominant d-form factor Fermi surface deformation and charge density wave order influenced by Coulomb interactions, aligning with experimental observations.

Contribution

It introduces a model with overlapping hot spots and Coulomb effects, showing a shift from charge modulation to Fermi surface deformation as the leading instability in cuprates.

Findings

Fermi surface deformation (Pomeranchuk instability) dominates at certain energies.

Charge density wave with d-form factor symmetry emerges at lower temperatures.

Remnant Coulomb interaction enhances the d-form factor charge density wave.

Abstract

We study particle-hole instabilities in the framework of the spin-fermion (SF) model. In contrast to previous studies, we assume that adjacent hot spots can overlap due to a shallow dispersion of the electron spectrum in the antinodal region. In addition, we take into account effects of a remnant low energy and momentum Coulomb interaction. We demonstrate that at sufficiently small values $|\varepsilon (\pi ,0)-E_{F}|\lesssim \Gamma $, where $E_{F}$ is the Fermi energy, $\varepsilon \left( \pi ,0\right) $ is the energy in the middle of the Brillouin zone edge, and $\Gamma $ is a characteristic energy of the fermion-fermion interaction due to the antiferromagnetic fluctuations, the leading particle-hole instability is a d-form factor Fermi surface deformation (Pomeranchuk instability) rather than the charge modulation along the Brillouin zone diagonals predicted within the standard SF model previously. At lower temperatures, we find that the deformed Fermi surface is further unstable to formation of a d-form factor charge density wave (CDW) with a wave vector along the Cu-O-Cu bonds (axes of the Brillouin zone). We show that the remnant Coulomb interaction enhances the d-form factor symmetry of the CDW. These findings can explain the robustness of this order in the cuprates. The approximations made in the paper are justified by a small parameter that allows one an Eliashberg-like treatment. Comparison with experiments suggests that in many cuprate compounds the prerequisites for the proposed scenario are indeed fulfilled and the results obtained may explain important features of the charge modulations observed recently.