Resonating bipolarons

TL;DR

This paper explores a resonant pairing mechanism between itinerant electrons and bipolarons in lattice systems, proposing a model analogous to Feshbach resonance to explain the transition between localized and itinerant electronic states.

Contribution

It introduces a novel resonant pairing framework to describe the crossover between itinerant electrons and bipolarons, supported by finite-size cluster simulations.

Findings

Resonant pairing can describe the crossover regime.

Finite-size clusters exhibit Feshbach-like resonance behavior.

Localized bipolarons and itinerant electrons are interconnected via resonance.

Abstract

Electrons coupled to local lattice deformations end up in selftrapped localized molecular states involving their binding into bipolarons when the coupling is stronger than a certain critical value. Below that value they exist as essentially itinerant electrons. We propose that the abrupt crossover between the two regimes can be described by resonant pairing similar to the Feshbach resonance in binary atomic collision processes. Given the intrinsically local nature of the exchange of pairs of itinerant electrons and localized bipolarons, we demonstrate the occurrence of such a resonance on a finite-size cluster made out of metallic atoms surrounding a polaronic ligand center.