The effect of dispersive optical phonons on the behaviour of a Holstein polaron

TL;DR

This paper investigates how dispersive optical phonons influence the properties of Holstein polarons, revealing that phonon dispersion significantly affects the polaron's effective mass at moderate and strong coupling regimes.

Contribution

It introduces an approximation-free Monte Carlo method to analyze the impact of phonon dispersion on Holstein polarons, highlighting the effect on effective mass variations.

Findings

Effective mass increases with negative phonon dispersion curvature.

Effect of phonon dispersion is negligible at weak coupling.

Significant impact observed at moderate and large electron-phonon coupling.

Abstract

We use the approximation-free Bold Diagrammatic Monte Carlo technique to study the effects of a finite dispersion of the optical phonon mode on the properties of the Holstein polaron, especially its effective mass. For weak electron-phonon coupling the effect is very small, but it becomes significant for moderate and large electron-phonon coupling. The effective mass is found to increase (decrease) if the phonon dispersion has a negative (positive) curvature at the centre of the Brillouin zone.