Effect of Adiabatic Phonons on Striped and Homogeneous Ground States

TL;DR

This study explores how adiabatic phonons influence the ground states of a spin-fermion model for high-temperature cuprates, revealing that electron-phonon interactions can stabilize or destabilize stripe formations and induce insulating or pseudogap states.

Contribution

It provides a detailed numerical analysis of how different phonon modes and electron-phonon couplings affect stripe stability and electronic properties in high T_c cuprates.

Findings

Strong diagonal EPI stabilizes stripes and induces an insulating gap.

Off-diagonal EPI destabilizes stripes, creating pseudogaps.

Breathing mode stabilizes static stripes; half-breathing and shear modes stabilize dynamic stripes.

Abstract

The effects of adiabatic phonons on a spin-fermion model for high T_c cuprates are studied using numerical simulations. In the absence of electron-phonon interactions (EPI), stripes in the ground state are observed for certain dopings while homogeneous states are stabilized in other regions of parameter space. Different modes of adiabatic phonons are added to the Hamiltonian:breathing, shear and half-breathing modes. Diagonal and off-diagonal electron-phonon couplings are considered. It is observed that strong diagonal EPI generate stripes in previously homogeneous states, while in striped ground states an increase in the diagonal couplings tends to stabilize the stripes, inducing a gap in the density of states (DOS) and rendering the ground state insulating. The off-diagonal terms, on the other hand, destabilize the stripes creating inhomogeneous ground states with a pseudogap at the chemical potential in the DOS. The breathing mode stabilizes static diagonal stripes; while the half-breathing (shear) modes stabilize dynamical (localized) vertical and horizontal stripes. The EPI induces decoherence of the quasi-particle peaks in the spectral functions.