Peierls transition in the presence of finite-frequency phonons in the one-dimensional extended Peierls-Hubbard model at half-filling

TL;DR

This study uses quantum Monte Carlo simulations to analyze the Mott insulator to Peierls insulator transition in a one-dimensional extended Hubbard model with finite-frequency phonons, revealing the critical electron-phonon coupling and its dependence on phonon frequency and electron-electron interactions.

Contribution

It provides the first detailed quantum Monte Carlo analysis of the finite-frequency phonon effects on the Mott-Peierls transition in a 1D extended Hubbard model, including phase boundary mapping.

Findings

Transition occurs at finite electron-phonon coupling.

Critical coupling depends on phonon frequency and electron-electron interactions.

Strong e-e interactions map to a spin-Peierls chain with comparable phase boundary.

Abstract

We report quantum Monte Carlo (stochastic series expansion) results for the transition from a Mott insulator to a dimerized Peierls insulating state in a half-filled, 1D extended Hubbard model coupled to optical bond phonons. Using electron-electron (e-e) interaction parameters corresponding approximately to polyacetylene, we show that the Mott-Peierls transition occurs at a finite value of the electron-phonon (e-ph) coupling. We discuss several different criteria for detecting the transition and show that they give consistent results. We calculate the critical e-ph coupling as a function of the bare phonon frequency and also investigate the sensitivity of the critical coupling to the strength of the e-e interaction. In the limit of strong e-e couplings, we map the model to a spin-Peierls chain and compare the phase boundary with previous results for the spin-Peierls transition. We point out effects of a nonlinear spin-phonon coupling neglected in the mapping to the spin-Peierls model.