Nature of extrinsic and intrinsic self-trapping of charge carriers in underdoped cuprate high-$T_\text{c}$ superconductors

TL;DR

This paper investigates the nature of self-trapping of charge carriers in underdoped cuprate high-temperature superconductors, calculating the properties of polarons and bipolarons to understand their role in superconductivity.

Contribution

It provides a theoretical analysis of extrinsic and intrinsic self-trapping, calculating binding energies and radii of polarons and bipolarons using a continuum model and adiabatic approximation.

Findings

Existence of 3D large bipolarons in underdoped cuprates at specific dielectric ratios.

Calculated binding energies and radii of polarons and bipolarons.

Conditions for bipolaron stability based on dielectric constants.

Abstract

Nature of extrinsic and intrinsic self-trapping (ST) of charge carriers in cuprates have been studied theoretically. The binding energies and radii of the extrinsic and intrinsic large polarons and bipolarons in cuprates are calculated variationally using the continuum model and adiabatic approximation. We have shown that the extrinsic and intrinsic three-dimensional (3D) large bipolarons exist in underdoped cuprates at $\eta=\varepsilon_{\infty}/\varepsilon_0<0.127$ and $\eta<0.138$, respectively [where $\varepsilon_{\infty}$ ($\varepsilon_0$) is the optic (static) dielectric constant].