Bond-Peierls polaron: Moderate mass enhancement and current-carrying ground state

TL;DR

This paper investigates one-dimensional Bond-Peierls polarons, revealing that phonon dispersion influences mass enhancement and ground state momentum, with implications for understanding electron-phonon interactions in low-dimensional systems.

Contribution

It demonstrates how phonon dispersion affects polaron mass and ground state properties in the Bond-Peierls model, contrasting with the Breathing-Mode Peierls problem.

Findings

Dispersionless phonons lead to localized polarons with infinite mass in the atomic limit.

Phonon dispersion results in finite polaron mass even in the atomic limit.

Depending on phonon dispersion, a transition to a non-zero-momentum ground state can occur.

Abstract

We study polarons in the one-dimensional Bond-Peierls electron-phonon model, in which phonons on bonds of a lattice modulate the hopping of electrons between lattice sites, and contrast the results to those known for the Breathing-Mode Peierls problem. By inspecting the atomic limit, we show that polaronic dressing and mass enhancement of Bond-Peierls polarons depend on the momentum dependence of the phonons. For dispersionless phonons, Bond-Peierls polarons are perfectly localized in the atomic limit, unlike their Breathing-mode counterparts, because the carrier creates a string of phonon excitations that can only be annihilated via processes that retrace the carrier to its original site. However, inclusion of phonon dispersion leads to a non-divergent polaron mass even in the atomic limit and depending on the form of the phonon dispersion may lead to a transition to a non-zero-momentum ground state akin to that found in the Breathing-mode Peierls model.