The breakdown of adiabatic polaron theory in one, two, and three dimensions and the reformation of the large polaron concept

TL;DR

This paper demonstrates that traditional adiabatic polaron theory fails at weak coupling across dimensions, leading to a revised understanding of large polarons and self-trapping phenomena.

Contribution

It provides a variational proof of correlated electron-phonon states that differ from adiabatic predictions, challenging established concepts in polaron physics.

Findings

Existence of correlated states below adiabatic ground states

Significant qualitative differences in correlation structures

Reevaluation of large polaron and self-trapping concepts

Abstract

We prove variationally that at weak coupling in one, two, and three dimensions there exist correlated electron-phonon states below the approximate ground states characteristically found by adiabatic polaron theory. Besides differing non-trivially in quantitative aspects such as the value of the ground state energy, these improved ground states are found to differ significantly in qualitative aspects such as correlation structure and scaling behavior. These differences are sufficiently severe as to require a reevaluation of the physical meaning attached to such widely used terms as "large polaron" and "self-trapping transition".