Large bipolarons and oxide superconductivity

TL;DR

This paper explores the concept of large-bipolaron superconductivity in oxides, highlighting how bipolarons form, condense into a liquid, and influence electrical properties, suggesting a plausible mechanism for oxide superconductivity at low carrier densities.

Contribution

It introduces a detailed theoretical model of large-bipolaron formation, condensation, and their role in oxide superconductivity, emphasizing the importance of dielectric constants and Coulomb interactions.

Findings

Large bipolarons can form at low carrier densities in oxides.

Condensed large-bipolaron liquids exhibit slow-moving excitations with high effective mass.

A temperature-dependent energy gap influences electrical resistivity and excitations.

Abstract

Large-bipolaron superconductivity is plausible with carrier densities well below those of conventional metals. Bipolarons form when carriers self-trap in pairs. Coherently moving large-bipolarons require extremely large ratios of static to optical dielectric-constants. The mutual Coulomb repulsion of a planar large-bipolarons paired carriers drives it to a four-lobed shape. A phonon-mediated attraction among large-bipolarons propels their condensation into a liquid. This liquids excitations move slowly with a huge effective mass. Excitations concomitant weak scattering by phonons produces a moderate low-temperature dc resistivity that increases linearly with rising temperature. With falling temperature an energy gap opens between large-bipolarons excitations and those of their self-trapped electronic carriers.