Two-site polaron problem: a perturbation approach with variational basis states

TL;DR

This paper introduces a convergent perturbation method with a variational basis for analyzing a two-site polaron system across all electron-phonon coupling strengths, showing good agreement with exact results.

Contribution

It develops a novel perturbation approach using a modified Lang-Firsov transformation applicable throughout the entire coupling range.

Findings

Accurately computes single-electron energies and wave functions.

Demonstrates good agreement with exact solutions.

Applicable from antiadiabatic to intermediate coupling regimes.

Abstract

A convergent perturbation method using modified Lang Firsov transformation is developed for a two-site single-polaron system. The method is applicable for the entire range of the electron-phonon coupling strength from the antiadiabatic limit to the intermediate region of hopping. The single-electron energies, oscillator wave functions and correlation functions, calculated using this method, are in good agreement with the exact results.