Strongly bound yet light bipolarons for double-well electron-phonon coupling

TL;DR

This paper investigates a double-well electron-phonon coupling model using the Momentum Average approximation, revealing conditions under which strongly bound yet lightweight bipolarons can form, offering a new mechanism beyond traditional models.

Contribution

It introduces a novel double-well electron-phonon coupling model and demonstrates the existence of lightweight bipolarons in certain parameter regimes.

Findings

Strongly bound yet lightweight bipolarons predicted in the model

Identification of parameter regions supporting these bipolarons

Proposes a new mechanism for bipolaron formation

Abstract

We use the Momentum Average approximation (MA) to study the ground-state properties of strongly bound bipolarons in the double-well electron-phonon (el-ph) coupling model, which describes certain intercalated lattices where the linear term in the el-ph coupling vanishes due tosymmetry. We show that this model predicts the existence of strongly bound yet lightweight bipolarons in some regions of the parameter space. This provides a novel mechanism for the appearance of such bipolarons, in addition to long-range el-ph coupling and special lattice geometries.