Topological Doping of Correlated Insulators

TL;DR

This paper explores how doping correlated insulators leads to the formation of topological defects, such as solitons and domain walls, fundamentally altering their electronic states, with implications for materials like polyacetylene and cuprate superconductors.

Contribution

It provides a comprehensive review of topological defect generation in doped correlated insulators and distinguishes different mechanisms behind their electronic changes.

Findings

Doping induces topological defects like solitons and domain walls.

Experimental evidence of these features in cuprate superconductors.

Different mechanisms: Fermi surface instability vs Coulomb frustration.

Abstract

A material which is an insulator entirely because of interaction effects is called a correlated insulator. Examples are trans-polyacetylene and the cuprate high temperature superconductors. Whereas doping of a band insulator results in a shift of the chemical potential into the conduction or valence band, doping of a correlated insulator produces fundamental changes in the electronic density of states itself. We have found that a general feature of doping a correlated insulator is the generation of topological defects; solitons in one-dimension and anti-phase domain walls in higher dimensions. We review the well known features of this process in polyacetylene, and describe the experimental evidence that the analogous features are seen in the cuprate superconductors. We also distinguish the case in which the doping-induced features can be viewed as a Fermi surface instability, as in polyacetylene, and the more usual case in which they are a consequence of a Coulomb frustrated electronic tendency to phase separation. Paper presented at the Sixtieth Birthday Symposium for Alan J. Heeger, January 20, 1996