Large polaron formation induced by Rashba spin-orbit coupling

TL;DR

This paper investigates how Rashba spin-orbit coupling induces large polaron formation in a 2D electron-phonon system, revealing that even small spin-orbit interactions cause localization, with the localization length inversely related to the Rashba strength.

Contribution

It demonstrates that Rashba spin-orbit coupling causes delocalized electrons to localize into large polarons in a 2D Holstein model, a phenomenon not previously characterized.

Findings

Rashba coupling induces polaron formation from delocalized electrons.

Localization length is inversely proportional to Rashba coupling.

Large polaron state dominates a broad phase diagram region.

Abstract

Here the electron-phonon Holstein model with Rashba spin-orbit interaction is studied for a two dimensional square lattice in the adiabatic limit. It is demonstrated that a delocalized electron at zero spin-orbit coupling localizes into a large polaron state as soon as the Rashba term is nonzero. This spin-orbit induced polaron state has localization length inversely proportional to the Rashba coupling $\gamma$, and it dominates a wide region of the $\gamma$-$\lambda$ phase diagram, where $\lambda$ is the electron-phonon interaction.