Peierls versus Holstein models for describing electron-phonon coupling in perovskites

TL;DR

This study compares Peierls and Holstein models for electron-phonon interactions in perovskites, revealing that the Peierls model exhibits unique polaron dispersion features not captured by the Holstein model, emphasizing the need for careful model selection.

Contribution

It demonstrates that Peierls and Holstein models are not interchangeable for describing electron-phonon coupling in perovskite lattices, highlighting the importance of model choice based on polaron dispersion characteristics.

Findings

Peierls polaron dispersion shows sharp transitions in ground-state momentum.

Holstein polaron maintains a constant ground-state momentum.

Peierls and Holstein models are not equivalent across all parameter regimes.

Abstract

We use the Momentum Average approximation together with perturbative approaches, in the appropriate limits, to study the single polaron physics on a perovskite lattice inspired by BaBiO3. We investigate electron-phonon coupling of the Peierls type whereby the motion of ions modulates the values of the hopping integrals between sites, and show that it cannot be mapped onto the simpler one-band Holstein model in the whole parameter space. This is because the dispersion of the Peierls polaron has sharp transitions where the ground-state momentum jumps between high-symmetry points in the Brillouin zone, whereas the Holstein polaron always has the same ground-state momentum. These results imply that careful consideration is required to choose the appropriate model for carrier-lattice coupling in such complex lattices.