Polaron and Bipolaron Defects in a Charge Density Wave: a Model for Lightly Doped BaBiO3

Abstract

BaBiO3 is a prototype ``charge ordering system'' forming interpenetrating sublattices with nominal valence Bi(3+) and Bi(5+). It can also be regarded as a three-dimensional version of a Peierls insulator, the insulating gap being a consequence of an ordered distortion of oxygen atoms. When holes are added to BaBiO3 by doping, it remains insulating until a very large hole concentration is reached, at which point it becomes superconducting. The mechanism for insulating behavior of more lightly-doped samples is formation of small polarons or bipolarons. These are self-organized point defects in the Peierls order parameter, which trap carriers in bound states inside the Peierls gap. We calculate properties of the polarons and bipolarons using the Rice-Sneddon model. Bipolarons are the stable defect; the missing pair of electrons come from an empty midgap state built from the lower Peierls band. Each bipolaron distortion also pulls down six localized states below the bottom of the unoccupied upper Peierls band. The activation energy for bipolaron hopping is estimated.

9 pages with 8 embedded figures. See also cond-mat/0108089, a paper of 5 pages on the related topic of self-trapped excitons in BaBiO3

References in corpus (1)

• Self-Trapped Exciton Defects in a Charge Density Wave: Electronic Excitations of BaBiO3

Cited by in corpus (10)

• Momentum-Resolved Electronic Structure of the High-$T_c$ Superconductor Parent Compound BaBiO${}_3$
• Stability of Quantum Critical Points in the Presence of Competing Orders
• Bilayers of Rydberg atoms as a quantum simulator for unconventional superconductors
• Discontinuous polaron transition in a two-band model
• Model of the electron-phonon interaction and optical conductivity of Ba${}_{1-x}$K${}_x$BiO${}_3$ superconductors
• Peierls versus Holstein models for describing electron-phonon coupling in perovskites
• Mobile small bipolarons on a three-dimensional cubic lattice
• Self-Trapped Exciton Defects in a Charge Density Wave: Electronic Excitations of BaBiO3
• Topological (Sliced) Doping of a 3D Peierls System: Predicted Structure of Doped BaBiO3
• A microscopic modeling of phonon dynamics and charge response in metallic BaBiO${}_3$